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-185 Classe Rascunho
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.
Definição
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.
Impacto no mundo real
Real-world CVEs caused by CWE-185
-
Regexp isn't "anchored" to the beginning or end, which allows spoofed values that have trusted values as substrings.
-
Regexp for IP address isn't anchored at the end, allowing appending of shell metacharacters.
-
Bypass access restrictions via multiple leading slash, which causes a regular expression to fail.
-
Local user DoS via invalid regular expressions.
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chain: Malformed input generates a regular expression error that leads to information exposure.
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Certain strings are later used in a regexp, leading to a resultant crash.
-
MFV. Regular expression intended to protect against directory traversal reduces ".../...//" to "../".
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Malformed regexp syntax leads to information exposure in error message.
Como os atacantes a exploram
Trajeto do atacante passo a passo
- 1
The following code takes phone numbers as input, and uses a regular expression to reject invalid phone numbers.
- 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
This code uses a regular expression to validate an IP string prior to using it in a call to the "ping" command.
- 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.
Exemplo de código vulnerável
Vulnerable Perl
The following code takes phone numbers as input, and uses a regular expression to reject invalid phone numbers.
$phone = GetPhoneNumber();
if ($phone =~ /\d+-\d+/) {
```
# looks like it only has hyphens and digits*
system("lookup-phone $phone");}
else {
```
error("malformed number!");
} Exemplo 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 verificação de prevenção
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.
Sinais de deteção
How to detect CWE-185
O Plexicus deteta automaticamente o CWE-185 e abre um PR de correção em menos de 60 segundos.
O Codex Remedium analisa cada commit, identifica esta fraqueza exata e entrega um pull request pronto para revisão com o patch. Sem tickets. Sem transferências.
Perguntas frequentes O que é o CWE-185?
Qual a gravidade do CWE-185?
Que linguagens ou plataformas são afetadas pelo CWE-185?
Como posso prevenir o CWE-185?
Como é que o Plexicus deteta e corrige o CWE-185?
Onde posso saber mais sobre o CWE-185?
Frequently asked questions
O que é o 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.
Qual a gravidade do CWE-185?
A MITRE não publicou uma classificação de probabilidade de exploração para esta fraqueza. Trate-a como impacto médio até o seu modelo de ameaças provar o contrário.
Que linguagens ou plataformas são afetadas pelo CWE-185?
A MITRE não especificou as plataformas afetadas por este CWE — pode aplicar-se à maioria das stacks de aplicações.
Como posso prevenir o 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…
Como é que o Plexicus deteta e corrige o CWE-185?
O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-185 em cada commit. Quando é encontrada uma correspondência, o nosso agente Codex Remedium abre um PR de correção com o código corrigido, testes e um resumo de uma linha para o revisor.
Onde posso saber mais sobre o CWE-185?
A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/185.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.
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