Mojo::JWT versions before 1.02 for Perl verify HMAC signatures with a non-constant-time string comparison. The decode() method compares the supplied signature to the recomputed HMAC with Perl's eq operator, which stops at the first differing byte, so the comparison time varies with the number of matching leading bytes. A caller that decodes attacker supplied tokens leaks the expected signature through this timing variation, which can be aggregated over many requests to recover the signature and forge a token.
History

Thu, 23 Jul 2026 21:45:00 +0000

Type Values Removed Values Added
First Time appeared Jberger
Jberger mojo::jwt
Vendors & Products Jberger
Jberger mojo::jwt

Mon, 20 Jul 2026 20:30:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Fri, 17 Jul 2026 16:00:00 +0000

Type Values Removed Values Added
Description Mojo::JWT versions before 1.02 for Perl verify HMAC signatures with a non-constant-time string comparison. The decode() method compares the supplied signature to the recomputed HMAC with Perl's eq operator, which stops at the first differing byte, so the comparison time varies with the number of matching leading bytes. A caller that decodes attacker supplied tokens leaks the expected signature through this timing variation, which can be aggregated over many requests to recover the signature and forge a token.
Title Mojo::JWT versions before 1.02 for Perl verify HMAC signatures with a non-constant-time string comparison
Weaknesses CWE-208
References

cve-icon MITRE

Status: PUBLISHED

Assigner: CPANSec

Published: 2026-07-17T15:29:58.088Z

Updated: 2026-07-20T19:37:04.413Z

Reserved: 2026-05-25T20:46:44.842Z

Link: CVE-2026-9537

cve-icon Vulnrichment

Updated: 2026-07-17T17:25:14.154Z

cve-icon NVD

Status : Deferred

Published: 2026-07-17T16:17:20.417

Modified: 2026-07-20T20:16:47.960

Link: CVE-2026-9537

cve-icon Redhat

No data.