CWE-597 Variant Draft

Use of Wrong Operator in String Comparison

This vulnerability occurs when a developer incorrectly compares string values, typically by using reference equality operators (like == or !=) instead of dedicated string comparison methods (like…

Definition

What is CWE-597?

This vulnerability occurs when a developer incorrectly compares string values, typically by using reference equality operators (like == or !=) instead of dedicated string comparison methods (like .equals()).

In languages like Java, using '==' to compare strings checks if two object references point to the same memory location, not whether their textual content is identical. This is a common logic error because two separate string objects with the same characters will fail an '==' test, leading to unexpected program behavior and flawed conditional logic. While this often results in general bugs or incorrect functionality, it becomes a security issue when the flawed comparison is part of an authentication check, authorization decision, or input validation. An attacker could potentially bypass security controls by exploiting the unintended mismatch, turning a simple coding mistake into a system vulnerability.

Auswirkungen in der Praxis

Real-world CVEs caused by CWE-597

Bisher sind in MITREs Katalog keine öffentlichen CVE-Referenzen mit dieser CWE verknüpft.

Wie Angreifer es ausnutzen

Angreiferpfad Schritt für Schritt

1
In the example below, two Java String objects are declared and initialized with the same string values. An if statement is used to determine if the strings are equivalent.
2
However, the if statement will not be executed as the strings are compared using the "==" operator. For Java objects, such as String objects, the "==" operator compares object references, not object values. While the two String objects above contain the same string values, they refer to different object references, so the System.out.println statement will not be executed. To compare object values, the previous code could be modified to use the equals method:
3
In the example below, three JavaScript variables are declared and initialized with the same values. Note that JavaScript will change a value between numeric and string as needed, which is the reason an integer is included with the strings. An if statement is used to determine whether the values are the same.
4
However, the body of the if statement will not be executed, as the "===" compares both the type of the variable AND the value. As the types of the first comparison are number and string, it fails. The types in the second are int and reference, so this one fails as well. The types in the third are reference and string, so it also fails. While the variables above contain the same values, they are contained in different types, so the document.getElementById... statement will not be executed in any of the cases. To compare object values, the previous code is modified and shown below to use the "==" for value comparison so the comparison in this example executes the HTML statement:
5
In the example below, two PHP variables are declared and initialized with the same numbers - one as a string, the other as an integer. Note that PHP will change the string value to a number for a comparison. An if statement is used to determine whether the values are the same.

Verwundbares Codebeispiel

Vulnerable Java

In the example below, two Java String objects are declared and initialized with the same string values. An if statement is used to determine if the strings are equivalent.

Verwundbar Java

String str1 = new String("Hello");
  String str2 = new String("Hello");
  if (str1 == str2) {
  	System.out.println("str1 == str2");
  }

Sicheres Codebeispiel

Secure Java

However, the if statement will not be executed as the strings are compared using the "==" operator. For Java objects, such as String objects, the "==" operator compares object references, not object values. While the two String objects above contain the same string values, they refer to different object references, so the System.out.println statement will not be executed. To compare object values, the previous code could be modified to use the equals method:

Sicher Java

if (str1.equals(str2)) {
  	System.out.println("str1 equals str2");
  }

What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.

Präventions-Checkliste

How to prevent CWE-597

Implementation Within Java, use .equals() to compare string values. Within JavaScript, use == to compare string values. Within PHP, use == to compare a numeric value to a string value. (PHP converts the string to a number.)

Erkennungssignale

How to detect CWE-597

Automated Static Analysis High

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

CWE-597

Don't catalog this weakness. Prove it's reachable.

Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.

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Häufig gestellte Fragen

Frequently asked questions

Was ist CWE-597?

Wie gravierend ist CWE-597?

MITRE hat für diese Schwachstelle keine Exploit-Wahrscheinlichkeit veröffentlicht. Behandle sie als mittlere Auswirkung, bis dein Threat Model anderes belegt.

Welche Sprachen oder Plattformen sind von CWE-597 betroffen?

MITRE hat für diese CWE keine betroffenen Plattformen spezifiziert — sie kann in den meisten Anwendungs-Stacks auftreten.

Wie kann ich CWE-597 verhindern?

Within Java, use .equals() to compare string values. Within JavaScript, use == to compare string values. Within PHP, use == to compare a numeric value to a string value. (PHP converts the string to a number.)

Wie erkennt und behebt Plexicus CWE-597?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-597 bei jedem Commit. Bei einem Treffer öffnet unser Codex-Remedium-Agent einen Fix-PR mit korrigiertem Code, Tests und einer einzeiligen Zusammenfassung für den Reviewer.

Wo erfahre ich mehr über CWE-597?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/597.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

Weaknesses related to CWE-597

CWE-595 Parent

Comparison of Object References Instead of Object Contents

This vulnerability occurs when code incorrectly checks if two object references point to the same memory location, rather than comparing…

CWE-1097 Sibling

Persistent Storable Data Element without Associated Comparison Control Element

This weakness occurs when a persistent data object lacks the necessary methods to be properly compared, which can lead to inconsistent or…

Ressourcen

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