CWE-185 Classe Brouillon

Incorrect Regular Expression

This vulnerability occurs when a regular expression is written incorrectly, causing it to match or validate data in unintended and potentially dangerous ways.

Définition

What is CWE-185?

This vulnerability occurs when a regular expression is written incorrectly, causing it to match or validate data in unintended and potentially dangerous ways.
Incorrect regular expressions are a common source of security flaws because they often fail to properly filter or validate user input. When used in security controls—like input sanitization, access rules, or data validation—a flawed regex pattern can allow malicious data to slip through, bypassing critical protections. This can lead directly to injection attacks, authorization bypasses, or data corruption. Finding and fixing these subtle regex errors manually is time-consuming, especially in large codebases. While SAST tools can flag the problematic pattern, an ASPM platform like Plexicus uses AI to analyze the context and provide specific, automated remediation advice, helping developers apply the correct fix quickly and consistently across the entire application portfolio.
Impact réel

Real-world CVEs caused by CWE-185

  • CVE-2002-2109

    Regexp isn't "anchored" to the beginning or end, which allows spoofed values that have trusted values as substrings.

  • CVE-2005-1949

    Regexp for IP address isn't anchored at the end, allowing appending of shell metacharacters.

  • CVE-2001-1072

    Bypass access restrictions via multiple leading slash, which causes a regular expression to fail.

  • CVE-2000-0115

    Local user DoS via invalid regular expressions.

  • CVE-2002-1527

    chain: Malformed input generates a regular expression error that leads to information exposure.

  • CVE-2005-1061

    Certain strings are later used in a regexp, leading to a resultant crash.

  • CVE-2005-2169

    MFV. Regular expression intended to protect against directory traversal reduces ".../...//" to "../".

  • CVE-2005-0603

    Malformed regexp syntax leads to information exposure in error message.

Comment les attaquants l'exploitent

Parcours de l'attaquant étape par étape

  1. 1

    The following code takes phone numbers as input, and uses a regular expression to reject invalid phone numbers.

  2. 2

    An attacker could provide an argument such as: "; ls -l ; echo 123-456" This would pass the check, since "123-456" is sufficient to match the "\d+-\d+" portion of the regular expression.

  3. 3

    This code uses a regular expression to validate an IP string prior to using it in a call to the "ping" command.

  4. 4

    Since the regular expression does not have anchors (CWE-777), i.e. is unbounded without ^ or $ characters, then prepending a 0 or 0x to the beginning of the IP address will still result in a matched regex pattern. Since the ping command supports octal and hex prepended IP addresses, it will use the unexpectedly valid IP address (CWE-1389). For example, "0x63.63.63.63" would be considered equivalent to "99.63.63.63". As a result, the attacker could potentially ping systems that the attacker cannot reach directly.

Exemple de code vulnérable

Vulnerable Perl

The following code takes phone numbers as input, and uses a regular expression to reject invalid phone numbers.

Vulnérable Perl 
$phone = GetPhoneNumber();
  if ($phone =~ /\d+-\d+/) {
```
# looks like it only has hyphens and digits* 
  	system("lookup-phone $phone");} 
  else {
  ```
  	error("malformed number!");
  }
Exemple de code sécurisé

Secure pseudo

Sécurisé 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.
Liste de contrôle de prévention

How to prevent CWE-185

  • Architecture and Design Regular expressions can become error prone when defining a complex language even for those experienced in writing grammars. Determine if several smaller regular expressions simplify one large regular expression. Also, subject the regular expression to thorough testing techniques such as equivalence partitioning, boundary value analysis, and robustness. After testing and a reasonable confidence level is achieved, a regular expression may not be foolproof. If an exploit is allowed to slip through, then record the exploit and refactor the regular expression.
Signaux de détection

How to detect CWE-185

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.)

Correction automatique Plexicus

Plexicus détecte automatiquement CWE-185 et ouvre une PR de correction en moins de 60 secondes.

Codex Remedium analyse chaque commit, identifie cette faiblesse précise et livre une pull request prête à être relue avec le correctif. Pas de tickets. Pas de transferts.

Obtenir une démo Essayer Plexicus gratuitement
Questions fréquentes

Frequently asked questions

Qu'est-ce que CWE-185 ?

This vulnerability occurs when a regular expression is written incorrectly, causing it to match or validate data in unintended and potentially dangerous ways.

Quelle est la gravité de CWE-185 ?

MITRE n'a pas publié de note de probabilité d'exploitation pour cette faiblesse. Traitez-la comme un impact moyen jusqu'à ce que votre modèle de menace prouve le contraire.

Quels langages ou plateformes sont affectés par CWE-185 ?

MITRE n'a pas spécifié les plateformes affectées pour ce CWE — il peut s'appliquer à la plupart des stacks applicatives.

Comment puis-je prévenir CWE-185 ?

Regular expressions can become error prone when defining a complex language even for those experienced in writing grammars. Determine if several smaller regular expressions simplify one large regular expression. Also, subject the regular expression to thorough testing techniques such as equivalence partitioning, boundary value analysis, and robustness. After testing and a reasonable confidence level is achieved, a regular expression may not be foolproof. If an exploit is allowed to slip…

Comment Plexicus détecte et corrige CWE-185 ?

Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-185 à chaque commit. Lorsqu'une correspondance est trouvée, notre agent Codex Remedium ouvre une PR de correction avec le code corrigé, les tests et un résumé d'une ligne pour le relecteur.

Où puis-je en savoir plus sur CWE-185 ?

MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/185.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.

Faiblesses associées

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Ressources

Further reading

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