CWE

Common Weakness Enumeration

A Community-Developed List of Software Weakness Types

CWE/SANS Top 25 Most Dangerous Software Errors
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ID

CWE-624: Executable Regular Expression Error

Weakness ID: 624
Abstraction: Base
Status: Incomplete
Presentation Filter:
+ Description

Description Summary

The product uses a regular expression that either (1) contains an executable component with user-controlled inputs, or (2) allows a user to enable execution by inserting pattern modifiers.

Extended Description

Case (2) is possible in the PHP preg_replace() function, and possibly in other languages when a user-controlled input is inserted into a string that is later parsed as a regular expression.

+ Time of Introduction
  • Implementation
+ Applicable Platforms

Languages

PHP

Perl

+ Common Consequences
ScopeEffect
Confidentiality
Integrity
Availability

Technical Impact: Execute unauthorized code or commands

+ Observed Examples
ReferenceDescription
Executable regexp in PHP by inserting "e" modifier into first argument to preg_replace
Executable regexp in PHP by inserting "e" modifier into first argument to preg_replace
Complex curly syntax inserted into the replacement argument to PHP preg_replace(), which uses the "/e" modifier
Function allows remote attackers to execute arbitrary PHP code via the username field, which is used in a preg_replace function call with a /e (executable) modifier.
+ Potential Mitigations

Phase: Implementation

The regular expression feature in some languages allows inputs to be quoted or escaped before insertion, such as \Q and \E in Perl.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class77Improper Neutralization of Special Elements used in a Command ('Command Injection')
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory990SFP Secondary Cluster: Tainted Input to Command
Software Fault Pattern (SFP) Clusters (primary)888
+ Research Gaps

Under-studied. The existing PHP reports are limited to highly skilled researchers, but there are few examples for other languages. It is suspected that this is under-reported for all languages. Usability factors might make it more prevalent in PHP, but this theory has not been investigated.

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
Software Fault PatternsSFP24Tainted input to command
+ Content History
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Applicable_Platforms, Relationships, Observed_Example
2008-10-14CWE Content TeamMITREInternal
updated Description
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2012-05-11CWE Content TeamMITREInternal
updated Relationships
2012-10-30CWE Content TeamMITREInternal
updated Potential_Mitigations
2014-06-23CWE Content TeamMITREInternal
updated Observed_Examples
2014-07-30CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings

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Page Last Updated: January 18, 2017