CWE-627: Dynamic Variable Evaluation
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.
How it's found
Dynamic Variable Evaluation is a specific, narrowly defined instance of a broader pattern. Testers confirm it with targeted code review and a proof-of-concept input that exercises the exact code path this weakness describes.
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 functions.
Consequences
- Modify Application Data, Execute Unauthorized Code or Commands: An attacker could gain unauthorized access to internal program variables and execute arbitrary code.
Mitigations
- Implementation: Refactor the code to avoid dynamic variable evaluation whenever possible.
- Implementation: Use only allowlists of acceptable variable or function names.
- Implementation: For function names, ensure that you are only calling functions that accept the proper number of arguments, to avoid unexpected null arguments.
Where this fits in a TurboPentest engagement
This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.
Frequently asked questions
What is CWE-627?
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.
How do you find Dynamic Variable Evaluation?
Dynamic Variable Evaluation is a specific, narrowly defined instance of a broader pattern. Testers confirm it with targeted code review and a proof-of-concept input that exercises the exact code path this weakness describes.
What is the impact of CWE-627?
Modify Application Data, Execute Unauthorized Code or Commands: An attacker could gain unauthorized access to internal program variables and execute arbitrary code.
Does TurboPentest test for Dynamic Variable Evaluation?
This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.
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Written and reviewed by
Michel Chamberland - Founder & CEO, IntegSec
CISSP, OSCP, OSCE, CEH, GIAC, CCSK · 20+ years in offensive security
Michel has spent 20+ years on offensive security teams including IBM X-Force Red and Trustwave SpiderLabs, leading penetration tests, red team engagements, and breach response for Fortune 500 customers. He is the founder of IntegSec and the architect of TurboPentest.
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