CVE-2026-21713
MediumCVSS 5.9Exploitation Probability (EPSS)
Low risk32th percentile - higher than 32% of all known CVEs
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. This vulnerability affects 20.x, 22.x, 24.x, and 25.x.
Risk Assessment
An attacker with timing measurement capabilities could recover secret HMAC values, potentially leading to signature forgery and data integrity compromise.
Recommendation
Update Node.js to the latest patched version that provides constant-time comparisons.
Other vulnerabilities in Node.js
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Node.js versions 0.10.x before 0.10.42, 0.12.x before 0.12.10, 4.x before 4.3.0, and 5.x before 5.6.0 are vulnerable to HTTP request smuggling attacks via a crafted Content-Length HTTP header.
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Node.js versions 0.12.x before 0.12.9, 4.x before 4.2.3, and 5.x before 5.1.1 do not ensure the availability of a parser for each HTTP socket, allowing remote attackers to cause a denial of service via a pipelined HTTP request.
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Original NVD description (English source)
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**.