Vulnerability · Published Jun 29, 2026 · Assigned by CPANSec
CVE-2026-13758CryptX versions before 0.088_001 for Perl compare AEAD authentication tags in non-constant time in the streaming decrypt_done path
Low 3.7
In plain English
A low-severity security flaw in CryptX from MIK. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 34% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | libcryptx-perl | no fix listed | DEBIAN-CVE-2026-13758 |
| Debian:13 | libcryptx-perl | no fix listed | DEBIAN-CVE-2026-13758 |
| Debian:14 | libcryptx-perl | 0.089-1 | DEBIAN-CVE-2026-13758 |
| Ubuntu:25.10 | libcryptx-perl | no fix listed | UBUNTU-CVE-2026-13758 |
| Ubuntu:26.04:LTS | libcryptx-perl | no fix listed | UBUNTU-CVE-2026-13758 |
Affected products (as reported)
Weakness: CWE-208 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N