CVE-2026-9537 Details
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.
A timing side-channel vulnerability has been identified in Mojo::JWT versions prior to 1.02 for Perl. The issue arises in the decode() method, where HMAC signatures are verified using Perl's eq operator, leading to non-constant-time comparisons. This timing variation allows an attacker to infer the expected signature by measuring the response time, potentially enabling signature recovery and token forgery.
Users are advised to upgrade to Mojo::JWT version 1.02 or later, which addresses this vulnerability by using a constant-time comparison for HMAC signature verification.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Jul 17, 2026CISA-ADP
Assessed Jul 20, 2026References to Advisories, Solutions, and Tools
By selecting these links, you will be leaving this site. These are references gathered from the official CVE record and are not endorsed by Volerion.
| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/jberger/Mojo-JWT/commit/b8aefb846613e44b5b12bc170898ffd5b05094a2.patch | CPANSec | Source CodeVendor |
| http://www.openwall.com/lists/oss-security/2026/07/17/11 | CVE |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-208 | Observable Timing Discrepancy | CPANSec |
Affected Products
| Product | Versions |
|---|---|
| Mojo::JWT | < 1.02 |
CPE
Remediation
| |
Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 20, 2026 | CVE Modified | CISA-ADP |
| Jul 17, 2026 | CVE Modified | CVE |
| Jul 17, 2026 | New CVE Received | CPANSec |