CWE-624 Executable Regular Expression Error

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.

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.

• Confidentiality, Integrity, Availability: Execute Unauthorized Code or Commands

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

• 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.)

• CVE-2006-2059: Executable regexp in PHP by inserting "e" modifier into first argument to preg_replace • CVE-2005-3420: Executable regexp in PHP by inserting "e" modifier into first argument to preg_replace • CVE-2006-2878: Complex curly syntax inserted into the replacement argument to PHP preg_replace(), which uses the "/e" modifier • CVE-2006-2908: 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.