PT-2026-53736 · Mik · Cryptx
Stig Palmquist
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Published
2026-06-29
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Updated
2026-06-29
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CVE-2026-13758
None
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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.
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Weakness Enumeration
Related Identifiers
Affected Products
Cryptx