CVE-2026-9537

NameCVE-2026-9537
DescriptionMojo::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.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
libmojo-jwt-perl (PTS)bookworm, bullseye0.09-1vulnerable
trixie1.01-1vulnerable
forky, sid1.02-1fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
libmojo-jwt-perlsource(unstable)1.02-1

Notes

https://lists.security.metacpan.org/cve-announce/msg/41907805/
Fixed by: https://github.com/jberger/Mojo-JWT/commit/b8aefb846613e44b5b12bc170898ffd5b05094a2 (1.02)

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