Vulnerability Description
CryptX versions before 0.088_001 for Perl compare AEAD authentication tags in non-constant time in the streaming decrypt_done path. The decrypt_done($tag) form compares it against the computed tag with memNE (memcmp() != 0), which short-circuits on the first differing byte, so its run time depends on the number of matching leading bytes. This affects all five AEAD modes: GCM, CCM, ChaCha20Poly1305, EAX and OCB. The one-shot *_decrypt_verify helpers are unaffected; they verify the tag inside libtomcrypt with a constant-time comparison. The timing difference is a tag-verification oracle. An attacker who can submit many candidate tags for the same nonce, ciphertext and associated data while measuring the timing precisely enough may recover the expected tag byte by byte and forge a message that verifies.
CVSS Score
LOW
Related Weaknesses (CWE)
References
- https://github.com/DCIT/perl-CryptX/commit/7e56347d420aaf43b2ee1586f4a230492ccf1
- https://metacpan.org/release/MIK/CryptX-0.088_001/changes
- http://www.openwall.com/lists/oss-security/2026/06/29/19
FAQ
What is CVE-2026-13758?
CVE-2026-13758 is a vulnerability with a CVSS score of 3.7 (LOW). CryptX versions before 0.088_001 for Perl compare AEAD authentication tags in non-constant time in the streaming decrypt_done path. The decrypt_done($tag) form compares it against the computed tag wi...
How severe is CVE-2026-13758?
CVE-2026-13758 has been rated LOW with a CVSS base score of 3.7/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-13758?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.