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.
Analysis
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Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
|---|---|---|---|---|---|---|---|---|---|
| JBERGER | Mojo::JWT | unaffected |
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Vendor Solution
Upgrade to Mojo-JWT 1.02, which compares signatures with the constant-time Mojo::Util::secure_compare.
Tracking
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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 |
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Subscriptions
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MITRE
Status: PUBLISHED
Assigner: CPANSec
Published:
Updated: 2026-07-17T17:25:14.154Z
Reserved: 2026-05-25T20:46:44.842Z
Link: CVE-2026-9537
Vulnrichment
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NVD
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Redhat
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OpenCVE Enrichment
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