CVE-2026-21713
A flaw in Node.js HMAC verification uses a non-constant-time comparison when validating user-provided signatures, potentially leaking timing information proportional to the number of matching bytes. Under certain threat models where high-resolution timing measurements are possible, this behavior could be exploited as a timing oracle to infer HMAC values. Node.js already provides timing-safe comparison primitives used elsewhere in the codebase, indicating this is an oversight rather than an intentional design decision. This vulnerability affects **20.x, 22.x, 24.x, and 25.x**.
- Score
- CVSS 3.0 5.9 Medium
- Status
- Analyzed - support@hackerone.com
- Published
- 2026-03-30
- Last modified
- 2026-05-10
- Weaknesses
- CWE-208
Affected products
References
- https://nodejs.org/en/blog/vulnerability/march-2026-security-releases
