The product specifies a regular expression in a way that causes data to be improperly matched or compared.

What CVEs are caused by CWE-185?

22 recorded CVEs are attributed to CWE-185, including CVE-2024-2223, CVE-2026-25896, CVE-2026-27895.

How do you prevent 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 through, then record the exploit and refactor the regular expression.

How is CWE-185 detected?

Automated Static Analysis: 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.)

What are the consequences of CWE-185?

Exploiting CWE-185 can lead to: Unexpected State, Varies by Context, Bypass Protection Mechanism.

Is CWE-185 actively exploited?

22 recorded CVEs are caused by CWE-185; none are currently in CISA's KEV catalog of actively exploited flaws.

CWE-185: Incorrect Regular Expression

RadicalNotion.AI

Code examples

Illustrative examples from MITRE showing how the weakness appears in code.

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

Vulnerable example

perl

$phone = GetPhoneNumber();

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.

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

Vulnerable example

python

import subprocess

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.

CWE-185: Incorrect Regular Expression

Overview

Real-world CVEs

Common consequences

How it happens

When it is introduced

How to prevent it

How to detect it

Automated Static Analysis

Code examples

Illustrative examples

Terminology & mappings

Mapped taxonomies

Attack patterns

Frequently asked questions

References

Stay ahead of CWE-185

Overview

Real-world CVEs

Common consequences

How it happens

When it is introduced

How to prevent it

How to detect it

Automated Static Analysis

Code examples

Illustrative examples

Related weaknesses

Parent

Child

Can precede

Terminology & mappings

Mapped taxonomies

Attack patterns

Frequently asked questions

References

Stay ahead of CWE-185