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Δ / VULNERABILITY RECORD

CVE-2026-21637.

Source-reported disclosure and enrichment record.

SEVERITY / CVSSHIGH / 7.5No severity score in this snapshot.
EXPLOITATION STATUSNot listed in the cached KEV catalogThis does not establish absence of exploitation.
RECORD STATUSMicrosoft vendor recordModified Apr 14, 2026

Disclosure summary

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 for more information.

Source-reported weakness categories

CWE-400

Source-specific records & product guidance

Sources retain their own attribution and scoring. Follow the original record to confirm affected versions, fixed releases, and configuration conditions.

Microsoft Security Updates (CVRF) · 2026-Apr

Open original source · Updated Apr 14, 2026

HackerOne: CVE-2026-21637 TLS PSK/ALPN Callback Exceptions Bypass Error Handlers

Maximum of vendor-reported product scores; products and fixed builds are associations, not a universal affected-version statement.

Microsoft maximum product score: 7.5

VendorProduct / associationVersion / bounds
Microsoft update guideMicrosoft Visual Studio 2019 version 16.11 (includes 16.0 - 16.10) (MSRC status code 3)
Microsoft update guideMicrosoft Visual Studio 2022 version 17.12 (MSRC status code 3)
Microsoft update guideMicrosoft Visual Studio 2022 version 17.14 (MSRC status code 3)

Vendor remediation references

  • Release Notes · build 16.11.55 · product IDs 11935
  • Vendor guidance · product IDs 11935
  • Release Notes · build 17.12.19 · product IDs 12459
  • Vendor guidance · product IDs 12459
  • Release Notes · build 17.14.30 · product IDs 16767
  • Vendor guidance · product IDs 16767

Original records & references

PUBLISHED 2026-04-14T03:00:00-04:00
MODIFIED 2026-04-14T03:00:00-04:00
INGESTED 2026-10-08T12:45:03-04:00