CVE-2026-21637

Advisory lineage Upstream: 0 Downstream: 44
Analyzed
Published: 20 Jan 2026, 20:41
Last modified:21 Jan 2026, 20:22

Vulnerability Summary

Overall Risk (default)
medium
30/100
CVSS Score
7.5 HIGH
v3.1 (nvd)
EPSS Score
1.06% LOW
1% probability +1.01%
KEV
Not listed
Ransomware
No reports
Public exploits
None found
Dark Web
Not detected

Timeline

20 Jan 2026, 20:41
Published
Vulnerability first disclosed
21 Jan 2026, 20:22
Last Modified
Vulnerability information updated

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.

CVSS Metrics

  • v3.1•HIGH•Score: 7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  • v3.0•MEDIUM•Score: 5.9CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Trends

Current EPSS score: 1.06%• Percentile: 60%

Techniques & Countermeasures

  • CWE-400•Uncontrolled Resource Consumption

    The product does not properly control the allocation and maintenance of a limited resource.

Affected Systems

  • nodejs•node

    20.19.6 | 22.21.1 | 24.12.0 | 25.2.1 | ≥ 4.0, < 4.* | ≥ 5.0, < 5.* | ≥ 6.0, < 6.* | ≥ 7.0, < 7.* | ≥ 8.0, < 8.* | ≥ 9.0, < 9.* | ≥ 10.0, < 10.* | ≥ 11.0, < 11.* | ≥ 12.0, < 12.* | ≥ 13.0, < 13.* | ≥ 14.0, < 14.* | ≥ 15.0, < 15.* | ≥ 16.0, < 16.* | ≥ 17.0, < 17.* | ≥ 18.0, < 18.*

  • nodejs•node.js

    ≥ 4.0.0, < 20.20.0 | ≥ 22.0.0, < 22.22.0 | ≥ 24.0.0, < 24.13.0 | ≥ 25.0.0, < 25.3.0

References (1)