CVE-2026-21637

HIGHNVD 7.55.9▼
EchelonGraph scoreMEDIUM confidence

Score 5.9 from GitHub Security Advisory published 2026-01-20. NVD baseline CVSS 7.5; sources differ by 1.6.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 7.5Exploit: NoneExposed: 0

A fix is available — apply it.

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 v3
7.5
EG Score
5.9(medium)
EPSS
60.9%
KEV
Not listed

Published

January 20, 2026

Last Modified

January 30, 2026

References (1)

Vendor Advisories for CVE-2026-21637(20)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(19)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatnodejs:24-8100020260408131901.6d8804032026-04-13redhat
redhatnodejs24-1:24.14.1-2.el10_12026-04-13redhat
redhatnodejs22-main-22.22.0-1.3.hum12026-04-10redhat
redhatnodejs20-main-20.20.0-7.1.hum12026-04-10redhat
redhatnodejs:24-9070020260402152654.rhel92026-04-09redhat
redhatnodejs25-main-25.9.0-1.hum12026-04-02redhat
redhatnodejs24-main-24.14.1-4.hum12026-04-01redhat
redhatnodejs22-1:22.22.0-1.el10_02026-02-18redhat
redhatnodejs:22-9060020260210120402.rhel92026-02-18redhat
redhatnodejs:22-9070020260117213838.rhel92026-02-17redhat
redhatnodejs:20-9070020260117213748.rhel92026-02-17redhat
redhatnodejs:20-9060020260210180816.rhel92026-02-17redhat
redhatnodejs:20-9040020260211171433.rhel92026-02-17redhat
redhatnodejs:24-9070020260117213814.rhel92026-02-17redhat
redhatnodejs:22-8100020260119091831.6d8804032026-02-10redhat
redhatnodejs:24-8100020260116121421.6d8804032026-02-10redhat
redhatnodejs:20-8100020260119100525.489197e62026-02-10redhat
redhatnodejs22-1:22.22.0-3.el10_12026-02-05redhat
redhatnodejs24-1:24.13.0-1.el10_12026-02-05redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 12× in last 7d / 45× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-22 14:08 UTCEPSS rescore
  2. 2026-07-21 15:24 UTCEPSS rescore
  3. 2026-07-21 15:24 UTCEPSS rescore
  4. 2026-07-20 17:08 UTCEPSS rescore
  5. 2026-07-19 14:31 UTCEPSS rescore
  6. 2026-07-19 14:31 UTCEPSS rescore
  7. 2026-07-19 02:29 UTCEPSS rescore
  8. 2026-07-19 02:28 UTCEPSS rescore
  9. 2026-07-18 10:04 UTCEPSS rescore
  10. 2026-07-18 10:04 UTCEPSS rescore
  11. 2026-07-16 17:03 UTCEPSS rescore
  12. 2026-07-16 17:03 UTCEPSS rescore
  13. 2026-07-15 16:57 UTCEPSS rescore
  14. 2026-07-15 16:57 UTCEPSS rescore
  15. 2026-07-15 02:00 UTCEPSS rescore
  16. 2026-07-15 02:00 UTCEPSS rescore
  17. 2026-07-13 22:30 UTCEPSS rescore
  18. 2026-07-13 06:13 UTCEPSS rescore
  19. 2026-07-13 06:13 UTCEPSS rescore
  20. 2026-07-12 05:46 UTCEPSS rescore
  21. 2026-07-12 05:46 UTCEPSS rescore
  22. 2026-07-11 08:27 UTCEPSS rescore
  23. 2026-07-09 19:10 UTCEPSS rescore
  24. 2026-07-08 15:15 UTCEPSS rescore
  25. 2026-07-08 15:15 UTCEPSS rescore
Show 64 more
  1. 2026-07-07 13:46 UTCEPSS rescore
  2. 2026-07-06 16:27 UTCEPSS rescore
  3. 2026-07-06 16:27 UTCEPSS rescore
  4. 2026-07-06 05:02 UTCOSV refresh
  5. 2026-07-06 02:23 UTCEPSS rescore
  6. 2026-07-06 02:23 UTCEPSS rescore
  7. 2026-07-05 02:30 UTCEPSS rescore
  8. 2026-07-04 06:31 UTCEPSS rescore
  9. 2026-07-04 06:31 UTCEPSS rescore
  10. 2026-07-01 15:06 UTCEPSS rescore
  11. 2026-07-01 15:06 UTCEPSS rescore
  12. 2026-06-30 23:22 UTCEPSS rescore
  13. 2026-06-29 14:06 UTCEPSS rescore
  14. 2026-06-28 14:07 UTCEPSS rescore
  15. 2026-06-28 04:56 UTCEPSS rescore
  16. 2026-06-28 04:56 UTCEPSS rescore
  17. 2026-06-27 03:08 UTCEPSS rescore
  18. 2026-06-25 13:49 UTCEPSS rescore
  19. 2026-06-24 14:05 UTCEPSS rescore
  20. 2026-06-23 21:32 UTCEPSS rescore
  21. 2026-06-22 14:25 UTCEPSS rescore
  22. 2026-06-22 14:25 UTCEPSS rescore
  23. 2026-06-21 14:56 UTCEPSS rescore
  24. 2026-06-21 14:56 UTCEPSS rescore
  25. 2026-06-21 01:59 UTCEPSS rescore
  26. 2026-06-21 01:59 UTCEPSS rescore
  27. 2026-06-19 19:25 UTCEPSS rescore
  28. 2026-06-18 17:52 UTCEPSS rescore
  29. 2026-06-17 17:53 UTCEPSS rescore
  30. 2026-06-17 16:35 UTCOSV refresh
  31. 2026-06-16 17:52 UTCEPSS rescore
  32. 2026-06-15 17:48 UTCEPSS rescore
  33. 2026-06-14 23:18 UTCEPSS rescore
  34. 2026-06-13 23:00 UTCEPSS rescore
  35. 2026-06-13 23:00 UTCEPSS rescore
  36. 2026-06-12 23:12 UTCEPSS rescore
  37. 2026-06-11 14:00 UTCEPSS rescore
  38. 2026-06-10 22:18 UTCEPSS rescore
  39. 2026-06-10 13:22 UTCEPSS rescore
  40. 2026-06-08 14:17 UTCEPSS rescore
  41. 2026-06-08 14:17 UTCEPSS rescore
  42. 2026-06-07 15:25 UTCEPSS rescore
  43. 2026-06-07 15:24 UTCEPSS rescore
  44. 2026-06-06 13:47 UTCEPSS rescore
  45. 2026-06-06 13:47 UTCEPSS rescore
  46. 2026-06-06 13:47 UTCEPSS rescore
  47. 2026-06-05 22:47 UTCEPSS rescore
  48. 2026-06-05 06:10 UTCEPSS rescore
  49. 2026-06-05 06:10 UTCEPSS rescore
  50. 2026-06-02 20:13 UTCEPSS rescore
  51. 2026-06-02 20:13 UTCEPSS rescore
  52. 2026-06-01 13:51 UTCEPSS rescore
  53. 2026-06-01 13:51 UTCEPSS rescore
  54. 2026-06-01 13:51 UTCEPSS rescore
  55. 2026-05-31 22:30 UTCEPSS rescore
  56. 2026-05-31 22:30 UTCEPSS rescore
  57. 2026-05-31 00:16 UTCEPSS rescore
  58. 2026-05-31 00:16 UTCEPSS rescore
  59. 2026-05-31 00:16 UTCEPSS rescore
  60. 2026-05-29 15:34 UTCEG score recompute
  61. 2026-05-29 15:34 UTCVendor advisory
  62. 2026-05-29 15:34 UTCGHSA enrichment
  63. 2026-05-29 13:44 UTCEPSS rescore
  64. 2026-05-29 13:44 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2026-21637?
CVE-2026-21637 is a high vulnerability published on January 20, 2026. 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…
When was CVE-2026-21637 disclosed?
CVE-2026-21637 was first published in the National Vulnerability Database on January 20, 2026, with the most recent update on January 30, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-21637 actively exploited?
CVE-2026-21637 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 60.9% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-21637?
CVE-2026-21637 has a CVSS v3 base score of 7.5 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 5.9.
How do I remediate CVE-2026-21637?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-21637, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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