Description

The software validates input before applying protection mechanisms that modify the input, which could allow an attacker to bypass the validation via dangerous inputs that only arise after the modification.

Software needs to validate data at the proper time, after data has been canonicalized and cleansed. Early validation is susceptible to various manipulations that result in dangerous inputs that are produced by canonicalization and cleansing.

Modes of Introduction:

– Implementation

Related Weaknesses

CWE-20
CWE-696

Consequences

Access Control, Integrity: Bypass Protection Mechanism, Execute Unauthorized Code or Commands

An attacker could include dangerous input that bypasses validation protection mechanisms which can be used to launch various attacks including injection attacks, execute arbitrary code or cause other unintended behavior.

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-2000-0191
  • Overlaps “fakechild/../realchild”

• CVE-2004-2363
  • Product checks URI for “

• CVE-2002-0934
  • Directory traversal vulnerability allows remote attackers to read or modify arbitrary files via invalid characters between two . (dot) characters, which are filtered and result in a “..” sequence.

• CVE-2003-0282
  • Directory traversal vulnerability allows attackers to overwrite arbitrary files via invalid characters between two . (dot) characters, which are filtered and result in a “..” sequence.