CVE-2021-42340

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 11.0%, top 5% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Trending — 3 sources updated this weekElevated
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 11%CVSS: 7.5Exploit: NoneExposed: 0

A fix is available — apply it.

The fix for bug 63362 present in Apache Tomcat 10.1.0-M1 to 10.1.0-M5, 10.0.0-M1 to 10.0.11, 9.0.40 to 9.0.53 and 8.5.60 to 8.5.71 introduced a memory leak. The object introduced to collect metrics for HTTP upgrade connections was not released for WebSocket connections once the connection was closed. This created a memory leak that, over time, could lead to a denial of service via an OutOfMemoryError.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
—
EPSS
95.4%
KEV
Not listed

Published

October 14, 2021

Last Modified

November 21, 2024

References (18)

Vendor Advisories for CVE-2021-42340(1)

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

Patch Availability(3)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatpki-servlet-engine-1:9.0.50-1.el92022-11-15redhat
redhattomcat2022-07-07redhat
redhatjws5-tomcat-vault-0:1.1.8-4.Final_redhat_00004.1.el8jws2021-11-30redhat

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.

Affected Packages

(1 across 1 ecosystem)
Maven(1)
PackageVulnerable rangeFixed inDependents
org.apache.tomcat:tomcat8.5.60 ... 8.5.71 (10 versions)8.5.72—

Weakness Classification(1)

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

Additional Vendor Advisories

(4)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 12× in last 7d / 46× 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 22:51 UTCEG score recompute
  2. 2026-07-22 14:06 UTCEPSS rescore
  3. 2026-07-21 15:22 UTCEPSS rescore
  4. 2026-07-21 15:22 UTCEPSS rescore
  5. 2026-07-20 17:05 UTCEPSS rescore
  6. 2026-07-19 14:29 UTCEPSS rescore
  7. 2026-07-19 02:27 UTCEPSS rescore
  8. 2026-07-18 10:02 UTCEPSS rescore
  9. 2026-07-18 10:02 UTCEPSS rescore
  10. 2026-07-18 09:59 UTCOSV refresh
  11. 2026-07-16 17:00 UTCEPSS rescore
  12. 2026-07-16 17:00 UTCEPSS rescore
  13. 2026-07-15 16:55 UTCEPSS rescore
  14. 2026-07-15 16:55 UTCEPSS rescore
  15. 2026-07-15 01:58 UTCEPSS rescore
  16. 2026-07-13 22:27 UTCEPSS rescore
  17. 2026-07-13 22:27 UTCEPSS rescore
  18. 2026-07-12 05:44 UTCEPSS rescore
  19. 2026-07-11 08:25 UTCEPSS rescore
  20. 2026-07-11 08:25 UTCEPSS rescore
  21. 2026-07-09 19:07 UTCEPSS rescore
  22. 2026-07-08 15:12 UTCEPSS rescore
  23. 2026-07-07 13:43 UTCEPSS rescore
  24. 2026-07-06 16:25 UTCEPSS rescore
  25. 2026-07-06 16:25 UTCEPSS rescore
Show 70 more
  1. 2026-07-05 02:28 UTCEPSS rescore
  2. 2026-07-05 02:28 UTCEPSS rescore
  3. 2026-07-04 06:29 UTCEPSS rescore
  4. 2026-07-04 06:29 UTCEPSS rescore
  5. 2026-07-02 16:57 UTCEPSS rescore
  6. 2026-07-01 15:04 UTCEPSS rescore
  7. 2026-06-30 23:20 UTCEPSS rescore
  8. 2026-06-30 23:20 UTCEPSS rescore
  9. 2026-06-30 10:00 UTCOSV refresh
  10. 2026-06-29 14:04 UTCEPSS rescore
  11. 2026-06-28 14:05 UTCEPSS rescore
  12. 2026-06-28 04:54 UTCEPSS rescore
  13. 2026-06-28 04:54 UTCEPSS rescore
  14. 2026-06-27 03:06 UTCEPSS rescore
  15. 2026-06-27 03:06 UTCEPSS rescore
  16. 2026-06-25 13:48 UTCEPSS rescore
  17. 2026-06-25 13:48 UTCEPSS rescore
  18. 2026-06-24 14:03 UTCEPSS rescore
  19. 2026-06-24 14:03 UTCEPSS rescore
  20. 2026-06-23 21:31 UTCEPSS rescore
  21. 2026-06-23 21:31 UTCEPSS rescore
  22. 2026-06-22 14:24 UTCEPSS rescore
  23. 2026-06-21 14:55 UTCEPSS rescore
  24. 2026-06-21 01:58 UTCEPSS rescore
  25. 2026-06-21 01:58 UTCEPSS rescore
  26. 2026-06-19 19:24 UTCEPSS rescore
  27. 2026-06-19 19:24 UTCEPSS rescore
  28. 2026-06-18 17:51 UTCEPSS rescore
  29. 2026-06-18 17:51 UTCEPSS rescore
  30. 2026-06-17 17:51 UTCEPSS rescore
  31. 2026-06-17 17:51 UTCEPSS rescore
  32. 2026-06-17 17:51 UTCEPSS rescore
  33. 2026-06-16 17:51 UTCEPSS rescore
  34. 2026-06-16 17:51 UTCEPSS rescore
  35. 2026-06-15 17:46 UTCEPSS rescore
  36. 2026-06-13 22:58 UTCEPSS rescore
  37. 2026-06-13 22:58 UTCEPSS rescore
  38. 2026-06-12 23:10 UTCEPSS rescore
  39. 2026-06-12 19:10 UTCOSV refresh
  40. 2026-06-11 13:58 UTCEPSS rescore
  41. 2026-06-11 13:58 UTCEPSS rescore
  42. 2026-06-10 22:16 UTCEPSS rescore
  43. 2026-06-10 22:16 UTCEPSS rescore
  44. 2026-06-10 13:20 UTCEPSS rescore
  45. 2026-06-06 13:46 UTCEPSS rescore
  46. 2026-06-06 13:46 UTCEPSS rescore
  47. 2026-06-05 22:45 UTCEPSS rescore
  48. 2026-06-05 06:09 UTCEPSS rescore
  49. 2026-06-05 06:09 UTCEPSS rescore
  50. 2026-06-04 13:10 UTCEPSS rescore
  51. 2026-06-04 13:10 UTCEPSS rescore
  52. 2026-06-02 20:11 UTCEPSS rescore
  53. 2026-06-02 20:11 UTCEPSS rescore
  54. 2026-06-01 13:50 UTCEPSS rescore
  55. 2026-06-01 13:50 UTCEPSS rescore
  56. 2026-05-31 22:29 UTCEPSS rescore
  57. 2026-05-31 22:29 UTCEPSS rescore
  58. 2026-05-31 00:15 UTCEPSS rescore
  59. 2026-05-31 00:15 UTCEPSS rescore
  60. 2026-05-29 13:42 UTCEPSS rescore
  61. 2026-05-28 13:43 UTCEPSS rescore
  62. 2026-05-28 13:43 UTCEPSS rescore
  63. 2026-05-27 13:39 UTCEPSS rescore
  64. 2026-05-27 13:39 UTCEPSS rescore
  65. 2026-05-26 09:02 UTCEG score recompute
  66. 2026-05-26 09:02 UTCVendor advisory
  67. 2026-05-26 07:17 UTCEPSS rescore
  68. 2026-05-26 07:17 UTCEPSS rescore
  69. 2026-05-26 07:17 UTCEPSS rescore
  70. 2026-05-25 20:16 UTCOSV refresh

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Frequently asked(5)

What is CVE-2021-42340?
CVE-2021-42340 is a high vulnerability published on October 14, 2021. The fix for bug 63362 present in Apache Tomcat 10.1.0-M1 to 10.1.0-M5, 10.0.0-M1 to 10.0.11, 9.0.40 to 9.0.53 and 8.5.60 to 8.5.71 introduced a memory leak. The object introduced to collect metrics for HTTP upgrade connections was not released for WebSocket connections once the connection was…
When was CVE-2021-42340 disclosed?
CVE-2021-42340 was first published in the National Vulnerability Database on October 14, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-42340 actively exploited?
CVE-2021-42340 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 95.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-42340?
CVE-2021-42340 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2021-42340?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-42340, 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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