CVE-2026-21637 (CVSS 7.5 HIGH) is a Node.js TLS vulnerability where synchronous exceptions thrown within the `pskCallback` or `ALPNCallback` bypass standard error handlers, allowing a remote attacker to crash the server or cause resource exhaustion via file descriptor leaks during the TLS handshake. Affected versions are Node.js 4.0.0 through <20.20.0, 22.0.0 through <22.22.0, 24.0.0 through <24.13.0, and 25.0.0 through <25.3.0. The issue is resolved in versions 20.20.0, 22.22.0, 24.13.0, and 25.3.0.
[CVE-2026-21637](https://www.cve.org/CVERecord?id=CVE-2026-21637) is regarding a vulnerability 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. HackerOne created this CVE on their behalf. The documented Visual Studio updates incorporate updates in Node.js which address this vulnerability. Please see [CVE-2026-21637](https://www.cve.org/CVERecord?id=CVE-2026-21637) for more information.