Disclosure summary
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**.
Source-reported weakness categories
CWE-208
Source-specific records & product guidance
Sources retain their own attribution and scoring. Follow the original record to confirm affected versions, fixed releases, and configuration conditions.
Microsoft Security Updates (CVRF) · 2026-Mar
Open original source · Updated Apr 08, 2026
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**.
Maximum of vendor-reported product scores; products and fixed builds are associations, not a universal affected-version statement.
Microsoft maximum product score: 5.9
| Vendor | Product / association | Version / bounds |
|---|---|---|
| Microsoft update guide | azl3 nodejs 20.14.0-14 on Azure Linux 3.0 | (MSRC status code 3) |
| Microsoft update guide | azl3 nodejs24 24.13.0-3 on Azure Linux 3.0 | (MSRC status code 3) |
Vendor remediation references
- CBL-Mariner Releases · build 20.14.0-15 · product IDs 21111-17084
- Vendor guidance · product IDs 21111-17084
- CBL-Mariner Releases · build 24.14.1-1 · product IDs 21059-17084
- Vendor guidance · product IDs 21059-17084
Original records & references
- NIST NVD record
- CVE Program record
- msrc.microsoft.com — Vendor advisory
PUBLISHED 2026-03-31T21:19:42-04:00
MODIFIED 2026-04-08T21:39:52-04:00
INGESTED 2026-10-08T12:45:08-04:00