CVE-2026-6329 in wolfSSL
Summary
by MITRE • 06/26/2026
PKCS#12 MAC verification uses an attacker-controlled comparison length, weakening the integrity check on the MAC and allowing a mismatched MAC to be accepted. The PKCS#12 verify path compared the locally computed HMAC against the MAC parsed from the PKCS#12 structure using a length taken directly from the attacker-supplied input, without first verifying that it equals the length of the digest actually produced by the configured algorithm. A truncated or zero-length stored MAC could therefore be accepted, defeating the integrity protection of the MAC.
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Analysis
by VulDB Data Team • 06/26/2026
This vulnerability resides in the PKCS#12 cryptographic standard implementation where the Message Authentication Code verification process suffers from a critical flaw in how it handles length comparisons during MAC validation. The weakness occurs when the system compares a locally computed HMAC value against the MAC extracted from the PKCS#12 structure, utilizing a comparison length directly sourced from attacker-controlled input rather than validating it against the expected digest length of the configured algorithm.
The technical implementation flaw stems from improper input validation and sanitization practices within the cryptographic verification routine. When processing PKCS#12 files, the system parses the MAC value and its associated length field from the input structure without first confirming that this length matches the actual output length of the HMAC algorithm being used. This creates a scenario where an attacker can manipulate the length parameter to bypass the integrity check mechanism entirely.
This vulnerability directly maps to CWE-20, which covers improper input validation, and specifically relates to CWE-310, concerning cryptographic issues with insufficient verification of data integrity. The operational impact of this flaw is severe as it fundamentally undermines the security guarantees provided by PKCS#12's MAC protection mechanism. An attacker who can control the length parameter in a malformed PKCS#12 structure can effectively bypass the entire integrity check process and accept a mismatched or truncated MAC value.
The attack surface extends beyond simple data corruption to potentially enable more sophisticated attacks such as credential manipulation or unauthorized access to protected cryptographic materials. In environments where PKCS#12 files are used for certificate storage, key management, or secure configuration transfers, this vulnerability could allow adversaries to inject malicious content while maintaining the appearance of valid integrity protection.
From an ATT&CK perspective, this vulnerability aligns with techniques involving credential access and privilege escalation through manipulation of cryptographic verification processes. The flaw enables an attacker to perform integrity validation bypass attacks without requiring direct access to the underlying cryptographic keys or algorithms, making it particularly dangerous in scenarios where PKCS#12 files are processed automatically by systems.
Mitigation strategies should focus on implementing strict length validation before any MAC comparison occurs, ensuring that the length parameter extracted from the input structure matches exactly with the expected output length of the configured HMAC algorithm. Systems should also implement robust input sanitization and validation routines that prevent attacker-controlled parameters from influencing critical cryptographic operations. Additionally, regular updates to cryptographic libraries and implementations are essential to ensure that known vulnerabilities in PKCS#12 processing are addressed through proper code review and security testing practices.