CWE-638: Not Using Complete Mediation | Glexia
CWE-638 (Not Using Complete Mediation) weakness overview with consequences, detection methods, mitigations, related CVEs and MITRE ATT&CK context.
Glexia's Take · Automated analysis
CWE-638: Not Using Complete Mediation
Not Using Complete Mediation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Executive Impact
- Integrity Confidentiality Availability Access Control Other: Gain Privileges or Assume Identity Execute Unauthorized Code or Commands Bypass Protection Mechanism Read Application Data Other: A user might retain access to a critical resource even after privileges have been revoked, possibly allowing access to privileged functionality or sensitive information, depending on the role of the resource.
Developer Pattern
CWE-638 is the kind of defect developers can usually prevent with explicit validation, safer framework defaults, and tests that exercise hostile input or unsafe state transitions.
Automation confidence
high confidence from CWE-638, 4.20.
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Official CWE Definition
CWE-638: Not Using Complete Mediation
The product does not perform access checks on a resource every time the resource is accessed by an entity, which can create resultant weaknesses if that entity's rights or privileges change over time.
Developer And Remediation Guidance
How teams prevent and detect this weakness
Causes
- When executable library files are used on web servers, which is common in PHP applications, the developer might perform an access check in any user-facing executable, and omit the access check from the library file itself. By directly requesting the library file (CWE-425), an attacker can bypass this access check.
- When a developer begins to implement input validation for a web application, often the validation is performed in each area of the code that uses externally-controlled input. In complex applications with many inputs, the developer often misses a parameter here or a cookie there. One frequently-applied solution is to centralize all input validation, store these validated inputs in a separate data structure, and require that all access of those inputs must be through that data structure. An alternate approach would be to use an external input validation framework such as Struts, which performs the validation before the inputs are ever processed by the code.
Remediation
- Architecture and Design: Invalidate cached privileges, file handles or descriptors, or other access credentials whenever identities, processes, policies, roles, capabilities or permissions change. Perform complete authentication checks before accepting, caching and reusing data, dynamic content and code (scripts). Avoid caching access control decisions as much as possible.
- Architecture and Design: Identify all possible code paths that might access sensitive resources. If possible, create and use a single interface that performs the access checks, and develop code standards that require use of this interface.
Detection
- Code review
- SAST
- DAST
- Focused regression tests
Mappings
Related CVEs, CWEs, and ATT&CK context
Related CWEs
ATT&CK Relevance
ATT&CK relevance is shown only when reviewed or responsibly inferred.