CPANSA-Mojo-JWT-2026-9537: Mojo-JWT vulnerability

Publisher giterlizzi Document category csaf_security_advisory
Initial release date 2026-07-17T00:00:00 Engine CSAF Perl Toolkit 0.26
Current release date 2026-07-17T00:00:00 Build Date
Current version 1 Status final
CVSS v3.1 Base Score Severity
Original language Language en
Also referred to

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.

Vulnerabilities

CVE-2026-9537

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.

Weakness CWE-208 : Observable Timing Discrepancy

Product status

Known affected
Product Score
Mojo-JWT less than 1.02
CVSS Version CVSS Vector CVSS Base Score CVSS Base Severity
Fixed

giterlizzi

Namespace: https://github.com/giterlizzi/

gdt@cpan.org

References

Revision history

Version Date of the revision Summary of the revision
1 Fri Jul 17 00:00:00 2026 First release

Sharing rules

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