Vulnerability 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.
CVSS Score
MEDIUM
Related Weaknesses (CWE)
References
- https://github.com/jberger/Mojo-JWT/commit/b8aefb846613e44b5b12bc170898ffd5b0509
- http://www.openwall.com/lists/oss-security/2026/07/17/11
FAQ
What is CVE-2026-9537?
CVE-2026-9537 is a vulnerability with a CVSS score of 5.3 (MEDIUM). 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 op...
How severe is CVE-2026-9537?
CVE-2026-9537 has been rated MEDIUM with a CVSS base score of 5.3/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-9537?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.