CWE-180 Incorrect Behavior Order: Validate Before Canonicalize

The product validates input before it is canonicalized.

• Access Control: Bypass Protection Mechanism — This prevents the product from detecting data that becomes invalid after the canonicalization step. An attacker can bypass the validation and launch attacks that expose weaknesses that would otherwise be prevented, such as injection.

• [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.

• CVE-2002-0433: List files in web server using "*.ext" • 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-2000-0191: Overlaps "fakechild/../realchild" • 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.