Vulnerability in Mik Cryptx

CVE-2026-13758

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.

Published · last modified .

CVSS v3 metric

CVSS v3 base score 3.7 (Low). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N.

EPSS exploit prediction

EPSS: 0.004 (31.5th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 31st percentile — 31.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-13758: held from 0.004 to 0.004.

EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-13758?
CVE-2026-13758 is a low-severity vulnerability in Mik Cryptx, classified under CWE-208. CVSS score: 3.7/10. Published 2026-06-29.
How severe is CVE-2026-13758?
Low severity. CVSS v3 base score is 3.7 out of 10.