CVE-2026-21637: nodejs node · Uncontrolled Resource Consumption
Affects nodejs nodeSource CVE Database V5
Not known to be exploited · CVSS 5.9 Medium.
Data as of 26 Oct 2026, 08:30 UTC
- EPSS
- 1.1% chance of exploitation in 30 days – higher than 65% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 20 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| nodejsnode | Affected
| Fixed in– |
npmnodepkg:npm/nodeOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
European organizations should immediately audit their Node.js deployments to identify TLS servers using PSK or ALPN callbacks. Until official patches are released, developers should implement defensive coding practices by wrapping these callbacks in try-catch blocks to safely handle synchronous exceptions and prevent process crashes or resource leaks. Monitoring for abnormal process terminations or file descriptor usage can help detect exploitation attempts. Employing rate limiting and connection throttling on TLS handshake requests can reduce the risk of resource exhaustion. Organizations should also consider upgrading Node.js to versions where this issue is fixed once patches become available. Network-level protections such as Web Application Firewalls (WAFs) or intrusion prevention systems (IPS) can be tuned to detect and block suspicious TLS handshake patterns. Regularly reviewing Node.js release notes and security advisories will ensure timely application of fixes. Finally, implementing robust incident response plans for denial of service events will minimize operational impact.
Description
CVE-2026-21637 is a medium severity vulnerability in Node.js TLS error handling affecting multiple versions. It arises when synchronous exceptions thrown in PSK or ALPN callbacks during the TLS handshake bypass normal error handling, causing either immediate process termination or silent resource leaks. Remote attackers can exploit this by sending crafted TLS handshake requests, leading to denial of service through server crashes or resource exhaustion. No authentication or user interaction is required, and the flaw impacts TLS servers using these callbacks. Although no known exploits are reported in the wild yet, the vulnerability affects a wide range of Node.js versions, including recent releases. The CVSS score is 5.9, reflecting a moderate risk primarily to availability. European organizations running Node.