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.

Metrics

No CVSS v4.0

Attack Vector Network

Attack Complexity High

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

Attack Vector Network

Attack Complexity High

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v2

This CVE is not in the KEV list.

Exploitation none

Automatable yes

Technical Impact partial

Affected Vendors & Products

Vendors Products
Nodejs
  • Nodejs

No data.

No data.

References
Link Providers
https://www.spirityenterprise.com/pentest spirity
https://www.spirityenterprise.com/managed-detection-response spirity
https://www.spirityenterprise.com/virtual-ciso spirity
https://nodejs.org/en/blog/vulnerability/december-2025-security-releases cve-icon cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-21637 cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-21637 cve-icon
History

Wed, 21 Jan 2026 21:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-400
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Wed, 21 Jan 2026 12:15:00 +0000

Type Values Removed Values Added
Title nodejs: Nodejs denial of service
Weaknesses CWE-248
References
Metrics threat_severity

None

 cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Moderate

Wed, 21 Jan 2026 11:30:00 +0000

Type Values Removed Values Added
First Time appeared Nodejs
Nodejs nodejs
Vendors & Products Nodejs
Nodejs nodejs

Tue, 20 Jan 2026 20:45:00 +0000

Type Values Removed Values Added
Description 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.
References
Metrics cvssV3_0

{'score': 5.9, 'vector': 'CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'}
cve-icon MITRE

Status: PUBLISHED

Assigner: hackerone

Published:

Updated: 2026-01-21T20:22:51.033Z

Reserved: 2026-01-01T15:00:02.339Z

Link: CVE-2026-21637

cve-icon Vulnrichment

Updated: 2026-01-21T20:22:42.356Z

cve-icon NVD

Status : Received

Published: 2026-01-20T21:16:05.950

Modified: 2026-01-21T21:16:08.260

Link: CVE-2026-21637

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-01-20T20:41:55Z

Links: CVE-2026-21637 - Bugzilla