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Description
The software validates input before it is canonicalized, which prevents the software from detecting data that becomes invalid after the canonicalization step.
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.
Modes of Introduction:
– Implementation
Related Weaknesses
CWE-179
Consequences
Access Control: Bypass Protection Mechanism
Potential Mitigations
Phase: Implementation
Description:
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.
CVE References
- CVE-2002-0433
- Product allows remote attackers to view restricted files via an HTTP request containing a “*” (wildcard or asterisk) character.
- CVE-2003-0332
- Product modifies the first two letters of a filename extension after performing a security check, which allows remote attackers to bypass authentication via a filename with a .ats extension instead of a .hts extension.
- CVE-2002-0802
- Database consumes an extra character when processing a character that cannot be converted, which could remove an escape character from the query and make the application subject to SQL injection attacks.
- CVE-2004-2363
- Product checks URI for “<" and other literal characters, but does it before hex decoding the URI, so "%3E" and other sequences are allowed.
