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.
No advisories yet.
Solution
Upgrade to Mojo-JWT 1.02, which compares signatures with the constant-time Mojo::Util::secure_compare.
Workaround
No workaround given by the vendor.
Thu, 23 Jul 2026 21:45:00 +0000
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Jberger
Jberger mojo::jwt |
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| Vendors & Products |
Jberger
Jberger mojo::jwt |
Mon, 20 Jul 2026 20:30:00 +0000
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cvssV3_1
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Fri, 17 Jul 2026 16:00:00 +0000
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| 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 |
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Projects
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Status: PUBLISHED
Assigner: CPANSec
Published:
Updated: 2026-07-20T19:37:04.413Z
Reserved: 2026-05-25T20:46:44.842Z
Link: CVE-2026-9537
Updated: 2026-07-17T17:25:14.154Z
No data.
No data.
OpenCVE Enrichment
Updated: 2026-07-23T21:30:14Z