Node.js TLS Crash via PSK/ALPNCB Exceptions
CVE-2026-21637 Published on January 20, 2026
A flaw in Node.js TLS error handling allows remote attackers to crash or exhaust resources of a TLS server when `pskCallback` or `ALPNCallback` are in use. Synchronous exceptions thrown during these callbacks bypass standard TLS error handling paths (tlsClientError and error), causing either immediate process termination or silent file descriptor leaks that eventually lead to denial of service. Because these callbacks process attacker-controlled input during the TLS handshake, a remote client can repeatedly trigger the issue. This vulnerability affects TLS servers using PSK or ALPN callbacks across Node.js versions where these callbacks throw without being safely wrapped.
Weakness Type
What is a Resource Exhaustion Vulnerability?
The software does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources.
CVE-2026-21637 has been classified to as a Resource Exhaustion vulnerability or weakness.
Affected Versions
nodejs node:- Version 20.19.6, <= 20.19.6 is affected.
- Version 22.21.1, <= 22.21.1 is affected.
- Version 24.12.0, <= 24.12.0 is affected.
- Version 25.2.1, <= 25.2.1 is affected.
- Version 4.0 and below 4.* is affected.
- Version 5.0 and below 5.* is affected.
- Version 6.0 and below 6.* is affected.
- Version 7.0 and below 7.* is affected.
- Version 8.0 and below 8.* is affected.
- Version 9.0 and below 9.* is affected.
- Version 10.0 and below 10.* is affected.
- Version 11.0 and below 11.* is affected.
- Version 12.0 and below 12.* is affected.
- Version 13.0 and below 13.* is affected.
- Version 14.0 and below 14.* is affected.
- Version 15.0 and below 15.* is affected.
- Version 16.0 and below 16.* is affected.
- Version 17.0 and below 17.* is affected.
- Version 18.0 and below 18.* is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.