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Status: Incomplete Weakness ID: 627 (Weakness Base)Description Summary In a language where the user can influence the name of a variable at runtime, if the variable names are not controlled, an attacker can read or write to arbitrary variables, or access arbitrary functions. functions. Extended Description The resultant vulnerabilities depend on the behavior of the application, both at the crossover point and in any control/data flow that is reachable by the related variables or Alternate Terms Dynamic evaluation Potential Mitigations Avoid dynamic evaluation whenever possible. Use only whitelists of acceptable variable or function names. For function names, ensure that you are only calling functions that accept the proper number of arguments, to avoid unexpected null arguments. Background Details Many interpreted languages support the use of a "$$varname" construct to set a variable whose name is specified by the $varname variable. In PHP, these are referred to as "variable variables." Functions might also be invoked using similar syntax, such as $$funcname(arg1, arg2). Research Gaps Under-studied, probably under-reported. Few researchers look for this issue; most public reports are for PHP, although other languages are affected. This issue is likely to grow in PHP as developers begin to implement functionality in place of register_globals. References Steve Christey. "Dynamic Evaluation Vulnerabilities in PHP applications". Full-Disclosure. 2006-05-03. <http:/ Shaun Clowes. "A Study In Scarlet: Exploiting Common Vulnerabilities in PHP
Applications". <http:/ Relationships
Applicable Platforms Languages PHP Perl Time of Introduction  ImplementationContent History Modifications Eric Dalci. Cigital. 2008-07-01. (External) updated Time_of_Introduction CWE Content Team. MITRE. 2008-09-08. (Internal) updated Applicable_Platforms, Relationships CWE Content Team. MITRE. 2008-10-14. (Internal) updated Background_Details, Description |
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