CWE-180: Incorrect Behavior Order: Validate Before Canonicalize
The product validates input before it is canonicalized, which prevents the product from detecting data that becomes invalid after the canonicalization step.
How it's found
Incorrect Behavior Order: Validate Before Canonicalize 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.
This can be used by an attacker to bypass the validation and launch attacks that expose weaknesses that would otherwise be prevented, such as injection.
Vulnerable vs. safe
File f = new File(path);return f.getCanonicalPath();String path = getInputPath();if (path.startsWith("/safe_dir/")){}return f.getCanonicalPath();String path = getInputPath();File f = new File(path);if (f.getCanonicalPath().startsWith("/safe_dir/")){}Consequences
- Bypass Protection Mechanism
Mitigations
- Implementation: Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
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-180?
The product validates input before it is canonicalized, which prevents the product from detecting data that becomes invalid after the canonicalization step.
How do you find Incorrect Behavior Order: Validate Before Canonicalize?
Incorrect Behavior Order: Validate Before Canonicalize 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-180?
Bypass Protection Mechanism
Does TurboPentest test for Incorrect Behavior Order: Validate Before Canonicalize?
This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.
Related CWEs
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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