Mojo::JWT versions before 1.02 for Perl verify HMAC signatures with a non-constant-time string comparison

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-9537
StatePUBLISHED
AssignerCPANSec
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-17 16:17:20 UTC
Updated2026-07-20 20:16:47 UTC
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.

Risk And Classification

Primary CVSS: v3.1 5.3 MEDIUM from ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS: 0.001740000 probability, percentile 0.071090000 (date 2026-07-20)

Problem Types: CWE-208 | CWE-208 CWE-208 Observable Timing Discrepancy

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA JBERGER MojoJWT affected 1.02 custom Not specified

References

ReferenceSourceLinkTags
github.com/jberger/Mojo-JWT/commit/b8aefb846613e44b5b12bc170898ffd5b0509... 9b29abf9-4ab0-4765-b253-1875cd9b441e github.com
www.openwall.com/lists/oss-security/2026/07/17/11 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Additional Advisory Data

Solutions

CNA: Upgrade to Mojo-JWT 1.02, which compares signatures with the constant-time Mojo::Util::secure_compare.

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