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Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection')

Stable Base
Structure: Simple
Description

The product constructs all or part of an SQL command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended SQL command when it is sent to a downstream component. Without sufficient removal or quoting of SQL syntax in user-controllable inputs, the generated SQL query can cause those inputs to be interpreted as SQL instead of ordinary user data.

The product constructs all or part of an SQL command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended SQL command when it is sent to a downstream component. Without sufficient removal or quoting of SQL syntax in user-controllable inputs, the generated SQL query can cause those inputs to be interpreted as SQL instead of ordinary user data.
Common Consequences 5
Scope: ConfidentialityIntegrityAvailability

Impact: Execute Unauthorized Code or Commands

Adversaries could execute system commands, typically by changing the SQL statement to redirect output to a file that can then be executed.

Scope: Confidentiality

Impact: Read Application Data

Since SQL databases generally hold sensitive data, loss of confidentiality is a frequent problem with SQL injection vulnerabilities.

Scope: Authentication

Impact: Gain Privileges or Assume IdentityBypass Protection Mechanism

If poor SQL commands are used to check user names and passwords or perform other kinds of authentication, it may be possible to connect to the product as another user with no previous knowledge of the password.

Scope: Access Control

Impact: Bypass Protection Mechanism

If authorization information is held in a SQL database, it may be possible to change this information through the successful exploitation of a SQL injection vulnerability.

Scope: Integrity

Impact: Modify Application Data

Just as it may be possible to read sensitive information, it is also possible to modify or even delete this information with a SQL injection attack.
Detection Methods 9
Automated Static Analysis
This weakness can often be detected using automated static analysis tools. Many modern tools use data flow analysis or constraint-based techniques to minimize the number of false positives. Automated static analysis might not be able to recognize when proper input validation is being performed, leading to false positives - i.e., warnings that do not have any security consequences or do not require any code changes. Automated static analysis might not be able to detect the usage of custom API functions or third-party libraries that indirectly invoke SQL commands, leading to false negatives - especially if the API/library code is not available for analysis.
Automated Dynamic AnalysisModerate
This weakness can be detected using dynamic tools and techniques that interact with the software using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results.
Manual Analysis
Manual analysis can be useful for finding this weakness, but it might not achieve desired code coverage within limited time constraints. This becomes difficult for weaknesses that must be considered for all inputs, since the attack surface can be too large.
Automated Static Analysis - Binary or BytecodeHigh
According to SOAR [REF-1479], the following detection techniques may be useful: ``` Highly cost effective: ``` Bytecode Weakness Analysis - including disassembler + source code weakness analysis Binary Weakness Analysis - including disassembler + source code weakness analysis
Dynamic Analysis with Automated Results InterpretationHigh
According to SOAR [REF-1479], the following detection techniques may be useful: ``` Highly cost effective: ``` Database Scanners ``` Cost effective for partial coverage: ``` Web Application Scanner Web Services Scanner
Dynamic Analysis with Manual Results InterpretationSOAR Partial
According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Fuzz Tester Framework-based Fuzzer
Manual Static Analysis - Source CodeHigh
According to SOAR [REF-1479], the following detection techniques may be useful: ``` Highly cost effective: ``` Manual Source Code Review (not inspections) ``` Cost effective for partial coverage: ``` Focused Manual Spotcheck - Focused manual analysis of source
Automated Static Analysis - Source CodeHigh
According to SOAR [REF-1479], the following detection techniques may be useful: ``` Highly cost effective: ``` Source code Weakness Analyzer Context-configured Source Code Weakness Analyzer
Architecture or Design ReviewHigh
According to SOAR [REF-1479], the following detection techniques may be useful: ``` Highly cost effective: ``` Formal Methods / Correct-By-Construction ``` Cost effective for partial coverage: ``` Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)
Potential Mitigations 10
Phase: Architecture and Design

Strategy: Libraries or Frameworks

Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid [REF-1482]. For example, consider using persistence layers such as Hibernate or Enterprise Java Beans, which can provide significant protection against SQL injection if used properly.
Phase: Architecture and Design

Strategy: Parameterization

If available, use structured mechanisms that automatically enforce the separation between data and code. These mechanisms may be able to provide the relevant quoting, encoding, and validation automatically, instead of relying on the developer to provide this capability at every point where output is generated. Process SQL queries using prepared statements, parameterized queries, or stored procedures. These features should accept parameters or variables and support strong typing. Do not dynamically construct and execute query strings within these features using "exec" or similar functionality, since this may re-introduce the possibility of SQL injection. [REF-867]
Phase: Architecture and DesignOperation

Strategy: Environment Hardening

Run your code using the lowest privileges that are required to accomplish the necessary tasks [REF-76]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations. Specifically, follow the principle of least privilege when creating user accounts to a SQL database. The database users should only have the minimum privileges necessary to use their account. If the requirements of the system indicate that a user can read and modify their own data, then limit their privileges so they cannot read/write others' data. Use the strictest permissions possible on all database objects, such as execute-only for stored procedures.
Phase: Architecture and Design
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid Client-Side Enforcement of Server-Side Security. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
Phase: Implementation

Strategy: Output Encoding

While it is risky to use dynamically-generated query strings, code, or commands that mix control and data together, sometimes it may be unavoidable. Properly quote arguments and escape any special characters within those arguments. The most conservative approach is to escape or filter all characters that do not pass an extremely strict allowlist (such as everything that is not alphanumeric or white space). If some special characters are still needed, such as white space, wrap each argument in quotes after the escaping/filtering step. Be careful of argument injection (Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')). Instead of building a new implementation, such features may be available in the database or programming language. For example, the Oracle DBMS_ASSERT package can check or enforce that parameters have certain properties that make them less vulnerable to SQL injection. For MySQL, the mysql_real_escape_string() API function is available in both C and PHP.
Phase: Implementation

Strategy: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright. When constructing SQL query strings, use stringent allowlists that limit the character set based on the expected value of the parameter in the request. This will indirectly limit the scope of an attack, but this technique is less important than proper output encoding and escaping. Note that proper output encoding, escaping, and quoting is the most effective solution for preventing SQL injection, although input validation may provide some defense-in-depth. This is because it effectively limits what will appear in output. Input validation will not always prevent SQL injection, especially if you are required to support free-form text fields that could contain arbitrary characters. For example, the name "O'Reilly" would likely pass the validation step, since it is a common last name in the English language. However, it cannot be directly inserted into the database because it contains the "'" apostrophe character, which would need to be escaped or otherwise handled. In this case, stripping the apostrophe might reduce the risk of SQL injection, but it would produce incorrect behavior because the wrong name would be recorded. When feasible, it may be safest to disallow meta-characters entirely, instead of escaping them. This will provide some defense in depth. After the data is entered into the database, later processes may neglect to escape meta-characters before use, and you may not have control over those processes.
Phase: Architecture and Design

Strategy: Enforcement by Conversion

When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.
Phase: Implementation
Ensure that error messages only contain minimal details that are useful to the intended audience and no one else. The messages need to strike the balance between being too cryptic (which can confuse users) or being too detailed (which may reveal more than intended). The messages should not reveal the methods that were used to determine the error. Attackers can use detailed information to refine or optimize their original attack, thereby increasing their chances of success. If errors must be captured in some detail, record them in log messages, but consider what could occur if the log messages can be viewed by attackers. Highly sensitive information such as passwords should never be saved to log files. Avoid inconsistent messaging that might accidentally tip off an attacker about internal state, such as whether a user account exists or not. In the context of SQL Injection, error messages revealing the structure of a SQL query can help attackers tailor successful attack strings.
Phase: Operation

Strategy: Firewall

Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth [REF-1481.

Effectiveness: Moderate

Phase: OperationImplementation

Strategy: Environment Hardening

When using PHP, configure the application so that it does not use register_globals. During implementation, develop the application so that it does not rely on this feature, but be wary of implementing a register_globals emulation that is subject to weaknesses such as Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection'), Variable Extraction Error, and similar issues.
Demonstrative Examples 6
In 2008, a large number of web servers were compromised using the same SQL injection attack string. This single string worked against many different programs. The SQL injection was then used to modify the web sites to serve malicious code.

ID : DX-209

The following code dynamically constructs and executes a SQL query that searches for items matching a specified name. The query restricts the items displayed to those where owner matches the user name of the currently-authenticated user.

Code Example:

Bad
C#
c#
The query that this code intends to execute follows:

Code Example:

Informative
bash
However, because the query is constructed dynamically by concatenating a constant base query string and a user input string, the query only behaves correctly if itemName does not contain a single-quote character. If an attacker with the user name wiley enters the string:

Code Example:

Attack
bash
for itemName, then the query becomes the following:

Code Example:

Attack
bash
The addition of the:

Code Example:

Attack
bash
condition causes the WHERE clause to always evaluate to true, so the query becomes logically equivalent to the much simpler query:

Code Example:

Attack
bash
This simplification of the query allows the attacker to bypass the requirement that the query only return items owned by the authenticated user; the query now returns all entries stored in the items table, regardless of their specified owner.
This example examines the effects of a different malicious value passed to the query constructed and executed in the previous example.
If an attacker with the user name wiley enters the string:

Code Example:

Attack
bash
for itemName, then the query becomes the following two queries:

Code Example:

Attack
SQL
sql

--'*

Many database servers, including Microsoft(R) SQL Server 2000, allow multiple SQL statements separated by semicolons to be executed at once. While this attack string results in an error on Oracle and other database servers that do not allow the batch-execution of statements separated by semicolons, on databases that do allow batch execution, this type of attack allows the attacker to execute arbitrary commands against the database.
Notice the trailing pair of hyphens (--), which specifies to most database servers that the remainder of the statement is to be treated as a comment and not executed. In this case the comment character serves to remove the trailing single-quote left over from the modified query. On a database where comments are not allowed to be used in this way, the general attack could still be made effective using a trick similar to the one shown in the previous example.
If an attacker enters the string

Code Example:

Attack
bash
Then the following three valid statements will be created:

Code Example:

Attack
bash
One traditional approach to preventing SQL injection attacks is to handle them as an input validation problem and either accept only characters from an allowlist of safe values or identify and escape a denylist of potentially malicious values. Allowlists can be a very effective means of enforcing strict input validation rules, but parameterized SQL statements require less maintenance and can offer more guarantees with respect to security. As is almost always the case, denylisting is riddled with loopholes that make it ineffective at preventing SQL injection attacks. For example, attackers can:
- Target fields that are not quoted - Find ways to bypass the need for certain escaped meta-characters - Use stored procedures to hide the injected meta-characters.
Manually escaping characters in input to SQL queries can help, but it will not make your application secure from SQL injection attacks.
Another solution commonly proposed for dealing with SQL injection attacks is to use stored procedures. Although stored procedures prevent some types of SQL injection attacks, they do not protect against many others. For example, the following PL/SQL procedure is vulnerable to the same SQL injection attack shown in the first example.

Code Example:

Bad
SQL
sql
Stored procedures typically help prevent SQL injection attacks by limiting the types of statements that can be passed to their parameters. However, there are many ways around the limitations and many interesting statements that can still be passed to stored procedures. Again, stored procedures can prevent some exploits, but they will not make your application secure against SQL injection attacks.
MS SQL has a built in function that enables shell command execution. An SQL injection in such a context could be disastrous. For example, a query of the form:

Code Example:

Bad
SQL
sql
Where $user_input is taken from an untrusted source.
If the user provides the string:

Code Example:

Attack
bash
The query will take the following form:

Code Example:

Attack
bash
Now, this query can be broken down into:
1. a first SQL query: SELECT ITEM,PRICE FROM PRODUCT WHERE ITEM_CATEGORY=''; 1. a second SQL query, which executes the dir command in the shell: exec master..xp_cmdshell 'dir' 1. an MS SQL comment: --' ORDER BY PRICE
As can be seen, the malicious input changes the semantics of the query into a query, a shell command execution and a comment.
This code intends to print a message summary given the message ID.

Code Example:

Bad
PHP
php
The programmer may have skipped any input validation on $id under the assumption that attackers cannot modify the cookie. However, this is easy to do with custom client code or even in the web browser.
While $id is wrapped in single quotes in the call to mysql_query(), an attacker could simply change the incoming mid cookie to:

Code Example:

Attack
bash
This would produce the resulting query:

Code Example:

Result
bash
Not only will this retrieve message number 1432, it will retrieve all other messages.
In this case, the programmer could apply a simple modification to the code to eliminate the SQL injection:

Code Example:

Good
PHP
php
However, if this code is intended to support multiple users with different message boxes, the code might also need an access control check (Improper Authorization) to ensure that the application user has the permission to see that message.
This example attempts to take a last name provided by a user and enter it into a database.

Code Example:

Bad
Perl
perl

ensure only letters, hyphens and apostrophe are allowed*

perl
While the programmer applies an allowlist to the user input, it has shortcomings. First of all, the user is still allowed to provide hyphens, which are used as comment structures in SQL. If a user specifies "--" then the remainder of the statement will be treated as a comment, which may bypass security logic. Furthermore, the allowlist permits the apostrophe, which is also a data / command separator in SQL. If a user supplies a name with an apostrophe, they may be able to alter the structure of the whole statement and even change control flow of the program, possibly accessing or modifying confidential information. In this situation, both the hyphen and apostrophe are legitimate characters for a last name and permitting them is required. Instead, a programmer may want to use a prepared statement or apply an encoding routine to the input to prevent any data / directive misinterpretations.
Observed Examples 13
CVE-2023-32530SQL injection in security product dashboard using crafted certificate fields
CVE-2021-42258SQL injection in time and billing software, as exploited in the wild per CISA KEV.
CVE-2021-27101SQL injection in file-transfer system via a crafted Host header, as exploited in the wild per CISA KEV.
CVE-2020-12271SQL injection in firewall product's admin interface or user portal, as exploited in the wild per CISA KEV.
CVE-2019-3792An automation system written in Go contains an API that is vulnerable to SQL injection allowing the attacker to read privileged data.
CVE-2004-0366chain: SQL injection in library intended for database authentication allows SQL injection and authentication bypass.
CVE-2008-2790SQL injection through an ID that was supposed to be numeric.
CVE-2008-2223SQL injection through an ID that was supposed to be numeric.
CVE-2007-6602SQL injection via user name.
CVE-2008-5817SQL injection via user name or password fields.
CVE-2003-0377SQL injection in security product, using a crafted group name.
CVE-2008-2380SQL injection in authentication library.
CVE-2017-11508SQL injection in vulnerability management and reporting tool, using a crafted password.
References 20
NT Web Technology Vulnerabilities
rain.forest.puppy
Phrack Issue 54, Volume 8
25-12-1998
https://phrack.org/issues/54/8(2025-07-24)
ID: REF-1460
24 Deadly Sins of Software Security
Michael Howard, David LeBlanc, and John Viega
McGraw-Hill
2010
ID: REF-44
Writing Secure Code
Michael Howard and David LeBlanc
Microsoft Press
04-12-2002
https://www.microsoftpressstore.com/store/writing-secure-code-9780735617223
ID: REF-7
SQL Injection Prevention Cheat Sheet
OWASP
https://cheatsheetseries.owasp.org/cheatsheets/SQL_Injection_Prevention_Cheat_Sheet.html(2025-08-04)
ID: REF-867
SQL Injection Attacks by Example
Steven Friedl
10-10-2007
http://www.unixwiz.net/techtips/sql-injection.html
ID: REF-868
SQL Injection Cheat Sheet
Ferruh Mavituna
15-03-2007
https://web.archive.org/web/20080126180244/http://ferruh.mavituna.com/sql-injection-cheatsheet-oku/(2023-04-07)
ID: REF-869
The Database Hacker's Handbook: Defending Database Servers
David Litchfield, Chris Anley, John Heasman, and Bill Grindlay
Wiley
14-07-2005
ID: REF-870
The Oracle Hacker's Handbook: Hacking and Defending Oracle
David Litchfield
Wiley
30-01-2007
ID: REF-871
SQL Injection
Microsoft
12-2008
https://learn.microsoft.com/en-us/previous-versions/sql/sql-server-2008-r2/ms161953(v=sql.105)?redirectedfrom=MSDN(2023-04-07)
ID: REF-872
SQL Injection Attack
Microsoft Security Vulnerability Research & Defense
https://msrc.microsoft.com/blog/2008/05/sql-injection-attack/(2023-04-07)
ID: REF-873
Giving SQL Injection the Respect it Deserves
Michael Howard
15-05-2008
https://learn.microsoft.com/en-us/archive/blogs/michael_howard/giving-sql-injection-the-respect-it-deserves(2023-04-07)
ID: REF-874
Top 25 Series - Rank 2 - SQL Injection
Frank Kim
SANS Software Security Institute
01-03-2010
https://www.sans.org/blog/top-25-series-rank-2-sql-injection/(2023-04-07)
ID: REF-875
Least Privilege
Sean Barnum and Michael Gegick
14-09-2005
https://web.archive.org/web/20211209014121/https://www.cisa.gov/uscert/bsi/articles/knowledge/principles/least-privilege(2023-04-07)
ID: REF-76
The Art of Software Security Assessment
Mark Dowd, John McDonald, and Justin Schuh
Addison Wesley
2006
ID: REF-62
The Art of Software Security Assessment
Mark Dowd, John McDonald, and Justin Schuh
Addison Wesley
2006
ID: REF-62
Automated Source Code Security Measure (ASCSM)
Object Management Group (OMG)
01-2016
http://www.omg.org/spec/ASCSM/1.0/
ID: REF-962
Secure by Design Alert: Eliminating SQL Injection Vulnerabilities in Software
Cybersecurity and Infrastructure Security Agency
25-03-2024
https://www.cisa.gov/resources-tools/resources/secure-design-alert-eliminating-sql-injection-vulnerabilities-software(2024-07-14)
ID: REF-1447
State-of-the-Art Resources (SOAR) for Software Vulnerability Detection, Test, and Evaluation
Gregory Larsen, E. Kenneth Hong Fong, David A. Wheeler, and Rama S. Moorthy
07-2014
https://www.ida.org/-/media/feature/publications/s/st/stateoftheart-resources-soar-for-software-vulnerability-detection-test-and-evaluation/p-5061.ashx(2025-09-05)
ID: REF-1479
D3FEND: Application Layer Firewall
D3FEND
https://d3fend.mitre.org/dao/artifact/d3f:ApplicationLayerFirewall/(2025-09-06)
ID: REF-1481
D3FEND: D3-TL Trusted Library
D3FEND
https://d3fend.mitre.org/technique/d3f:TrustedLibrary/(2025-09-06)
ID: REF-1482
Likelihood of Exploit

High

Applicable Platforms
Languages:
Not Language-Specific : UndeterminedSQL : Often
Technologies:
Database Server : Undetermined
Modes of Introduction
Implementation
Implementation
Related Attack Patterns
Alternate Terms

SQL injection

a common attack-oriented phrase

SQLi

a common abbreviation for "SQL injection"
Related Weaknesses
ChildOf: Improper Neutralization of Special Elements in Data Query Logic (CWE-943)
ChildOf: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection') (CWE-74)
Taxonomy Mapping
  • PLOVER
  • 7 Pernicious Kingdoms
  • CLASP
  • OWASP Top Ten 2007
  • OWASP Top Ten 2004
  • OWASP Top Ten 2004
  • WASC
  • Software Fault Patterns
  • OMG ASCSM
  • SEI CERT Oracle Coding Standard for Java
Notes
RelationshipSQL injection can be resultant from special character mismanagement, MAID, or denylist/allowlist problems. It can be primary to authentication errors.