🛡️ CVE-2026-13758 on Ubuntu — libcryptx-perl

⚪ Unknown ✅ No Known Exploit OSV
N/A
CVSS Score
0 Low4 Medium7 High9 Critical10

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.

Distribution advisory

This page covers CVE-2026-13758 as tracked by Ubuntu, for the package libcryptx-perl. No fixed version has been recorded for this distribution yet.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality low, integrity none, availability none.

Affected software

UBUNTU-CVE-2026-13758 is recorded against 1 package.

  • libcryptx-perl

Timeline and source

Published on 29 June 2026 and last revised on 1 July 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

ubuntu.com (Report)
www.cve.org (Report)
lists.security.metacpan.org (Report)
github.com (Report)
metacpan.org (Report)
www.openwall.com (Report)

Details

Severity Unknown
CVSS Score N/A
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
CWE N/A
Public Exploit ✅ No
Source OSV
Published 2026-06-29
Updated 2026-08-11
Modified 2026-07-01
Fix URL N/A

Affected Packages

Software From version Fixed in
libcryptx-perl — —

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