Vulnerability Report

CVE-2026-21637

Title: DoS via TLS Error Handling in Node.js

DoS

Proof Of Concept

No public PoC currently indexed for CVE-2026-21637.

CWE Category NVD-CWE-noinfo

Published Date Jan 20, 2026

Modified Date Jan 30, 2026

Exploit Status Not Found

Score 7.5 CVSS v3.0

Exploit Probability (EPSS)

0.06%

Vulnerability Summary

CVE-2026-21637: 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.

Impacted Vendors

nodejs 1

joyent 1

Reference Links

https://nodejs.org/en/blog/vulnerability/december-2025-security-releases

CVSS v3.1

Source Entity [email protected]

Severity HIGH

7.5

Attack Vector

NETWORK

Complexity

LOW

Privileges

N/A

Interaction

NONE

Confidentiality

N/A

Integrity

N/A

Availability

N/A

Scope

UNCHANGED

RAW VECTOR CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.0