Exploitation of a vulnerability with commonly-used manipulations might fail, but minor variations might succeed.
CWE-184 Base Borrador
Incomplete List of Disallowed Inputs
This vulnerability occurs when a security filter or validation mechanism relies on a 'denylist'—a predefined list of forbidden inputs—but that list is missing critical entries. Attackers can bypass…
Definición
What is CWE-184?
This vulnerability occurs when a security filter or validation mechanism relies on a 'denylist'—a predefined list of forbidden inputs—but that list is missing critical entries. Attackers can bypass the protection by using variations or inputs the developers didn't anticipate.
Denylist-based security is fundamentally fragile because it requires developers to predict and block every possible bad input. This approach often fails against sophisticated attacks, as attackers constantly evolve their techniques to use new encodings, character sequences, or command variations that aren't on the list. Relying solely on a denylist creates a false sense of security and is difficult to maintain over time.
For stronger protection, prioritize 'allowlisting' (only permitting known-good patterns) over denylisting. If a denylist is unavoidable, complement it with other defenses like strict input validation, output encoding, and security libraries designed to handle the specific threat. Always assume your denylist is incomplete and design your system to fail safely when an unexpected input is encountered.
Impacto en el mundo real
Real-world CVEs caused by CWE-184
-
Chain: API for text generation using Large Language Models (LLMs) does not include the "\" Windows folder separator in its denylist (CWE-184) when attempting to prevent Local File Inclusion via path traversal (CWE-22), allowing deletion of arbitrary files on Windows systems.
-
product uses a denylist to identify potentially dangerous content, allowing attacker to bypass a warning
-
PHP remote file inclusion in web application that filters "http" and "https" URLs, but not "ftp".
-
Programming language does not filter certain shell metacharacters in Windows environment.
-
XSS filter doesn't filter null characters before looking for dangerous tags, which are ignored by web browsers. MIE and validate-before-cleanse.
-
Web-based mail product doesn't restrict dangerous extensions such as ASPX on a web server, even though others are prohibited.
-
Resultant XSS when only and are checked.
-
Privileged program does not clear sensitive environment variables that are used by bash. Overlaps multiple interpretation error.
Cómo lo explotan los atacantes
Ruta del atacante paso a paso
- 1
Identifica una ruta de código que maneje entrada no confiable sin validación.
- 2
Crea un payload que ejercite el comportamiento inseguro — inyección, traversal, overflow o abuso de lógica.
- 3
Envía el payload a través de una solicitud normal y observa la reacción de la aplicación.
- 4
Itera hasta que la respuesta filtre datos, ejecute código del atacante o escale privilegios.
Ejemplo de código vulnerable
Vulnerable Java
The following code attempts to stop XSS attacks by removing all occurences of "script" in an input string.
public String removeScriptTags(String input, String mask) {
return input.replaceAll("script", mask);
} Ejemplo de código seguro
Secure pseudo
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
const safe = validateAndEscape(input);
return executeWithGuards(safe);
} What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Lista de prevención
How to prevent CWE-184
- Implementation Do not rely exclusively on detecting disallowed inputs. There are too many variants to encode a character, especially when different environments are used, so there is a high likelihood of missing some variants. Only use detection of disallowed inputs as a mechanism for detecting suspicious activity. Ensure that you are using other protection mechanisms that only identify "good" input - such as lists of allowed inputs - and ensure that you are properly encoding your outputs.
Señales de detección
How to detect CWE-184
CWE-184
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.
Preguntas frecuentes ¿Qué es CWE-184?
¿Qué gravedad tiene CWE-184?
¿Qué lenguajes o plataformas se ven afectados por CWE-184?
¿Cómo puedo prevenir CWE-184?
¿Cómo detecta y corrige Plexicus CWE-184?
¿Dónde puedo aprender más sobre CWE-184?
Frequently asked questions
¿Qué es CWE-184?
This vulnerability occurs when a security filter or validation mechanism relies on a 'denylist'—a predefined list of forbidden inputs—but that list is missing critical entries. Attackers can bypass the protection by using variations or inputs the developers didn't anticipate.
¿Qué gravedad tiene CWE-184?
MITRE no ha publicado una calificación de probabilidad de explotación para esta debilidad. Trátala como de impacto medio hasta que tu modelo de amenazas demuestre lo contrario.
¿Qué lenguajes o plataformas se ven afectados por CWE-184?
MITRE no ha especificado plataformas afectadas para esta CWE — puede aplicar a la mayoría de los stacks de aplicaciones.
¿Cómo puedo prevenir CWE-184?
Do not rely exclusively on detecting disallowed inputs. There are too many variants to encode a character, especially when different environments are used, so there is a high likelihood of missing some variants. Only use detection of disallowed inputs as a mechanism for detecting suspicious activity. Ensure that you are using other protection mechanisms that only identify "good" input - such as lists of allowed inputs - and ensure that you are properly encoding your outputs.
¿Cómo detecta y corrige Plexicus CWE-184?
El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-184 en cada commit. Cuando hay coincidencia, nuestro agente Codex Remedium abre un PR de corrección con el código corregido, las pruebas y un resumen de una línea para el revisor.
¿Dónde puedo aprender más sobre CWE-184?
MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/184.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.
Debilidades relacionadas
Weaknesses related to CWE-184
CWE-693 Padre
Protection Mechanism Failure
This weakness occurs when software either lacks a necessary security control, implements one that is too weak, or fails to activate an…
CWE-1039 Hermano
Inadequate Detection or Handling of Adversarial Input Perturbations in Automated Recognition Mechanism
This vulnerability occurs when a system uses automated AI or machine learning to classify complex inputs like images, audio, or text, but…
CWE-1248 Hermano
Semiconductor Defects in Hardware Logic with Security-Sensitive Implications
A security-critical hardware component contains physical flaws in its semiconductor material, which can cause it to malfunction and…
CWE-1253 Hermano
Incorrect Selection of Fuse Values
This vulnerability occurs when a hardware security fuse is incorrectly programmed to represent a 'secure' state as logic 0 (unblown). An…
CWE-1269 Hermano
Product Released in Non-Release Configuration
This vulnerability occurs when a product ships to customers while still configured with its pre-production or manufacturing settings,…
CWE-1278 Hermano
Missing Protection Against Hardware Reverse Engineering Using Integrated Circuit (IC) Imaging Techniques
This vulnerability occurs when hardware lacks safeguards against physical inspection, allowing attackers to extract sensitive data by…
CWE-1291 Hermano
Public Key Re-Use for Signing both Debug and Production Code
This vulnerability occurs when the same cryptographic key is used to sign both development/debug software builds and final production…
CWE-1318 Hermano
Missing Support for Security Features in On-chip Fabrics or Buses
This vulnerability occurs when the communication channels (fabrics or buses) within a chip lack built-in or enabled security features,…
CWE-1319 Hermano
Improper Protection against Electromagnetic Fault Injection (EM-FI)
This vulnerability occurs when a hardware device lacks sufficient shielding against electromagnetic interference, allowing attackers to…
Recursos
Further reading
¿Listo para validar lo que importa?
Listo para validar lo que importa.
Plexicus es Proof-Driven AppSec: hallazgos validados, comprensión contextual y remediación revisada — anclada en evidencia, acotada contigo.