CVE-2026-63495

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5%, top 57% 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, secondary
Trending — 3 sources updated this weekElevated
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 7.5Exploit: Elevated riskExposed: 0

A fix is available — apply it.

Libevent is an event notification library. From 2.2.0-alpha-dev until 2.2.2-alpha, the libevent WebSocket server in ws.c accumulates fragmented frames in evws->incomplete_frames without enforcing a total message-size limit. An unauthenticated remote client can repeatedly send fragmented WebSocket frames below WS_MAX_RECV_FRAME_SZ with FIN=0, causing the evbuffer to grow without bound until the process or host exhausts memory. This issue is fixed in version 2.2.2-alpha.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
65(Attend)
EG Risk 65/100SSVC: Attend

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity75% × 45%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
1%
EPSS %ILE
43%
KEV
Not listed

Published

August 20, 2026

Last Modified

September 9, 2026

Advisory Details (3)

Auto-updated Aug 20, 2026
🔬 Proof of concept available. Patch available. Sources: github, github_commit, github_release.
github_release Patch Available

Libevent 2.2.2-alpha

Patch available: libevent/libevent release-2.2.2-alpha

https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha
github_commit Patch Available

commit 291c4d1cd756 (libevent/libevent)

Patch available: libevent/libevent release-2.2.2-alpha (contains commit 291c4d1cd756)

https://github.com/libevent/libevent/commit/291c4d1cd75695e898030ebd5c4ddf26c094077b
github Patch Available🟡 PoC Available

Unbounded memory accumulation in WebSocket server via fragmented frames · Advisory · libevent/libevent · GitHub

https://github.com/libevent/libevent/security/advisories/GHSA-qx89-wf2v-vgmx

Vendor Advisories for CVE-2026-63495(1)

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

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatlibevent-main-2.1.12-19.hum12026-07-17redhat

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(2)

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

Data Freshness Timeline

(refreshed 25× in last 7d / 98× 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.

Showing the most recent 100 of 104 total refreshes for this CVE.

  1. 2026-09-20 23:57 UTCEG score recompute
  2. 2026-09-20 23:57 UTCVendor advisory
  3. 2026-09-20 20:16 UTCEPSS rescore
  4. 2026-09-20 12:01 UTCVendor advisory
  5. 2026-09-19 23:52 UTCEG score recompute
  6. 2026-09-19 23:52 UTCVendor advisory
  7. 2026-09-19 11:56 UTCVendor advisory
  8. 2026-09-19 00:00 UTCEG score recompute
  9. 2026-09-19 00:00 UTCVendor advisory
  10. 2026-09-18 19:28 UTCEPSS rescore
  11. 2026-09-18 12:04 UTCVendor advisory
  12. 2026-09-18 00:08 UTCEG score recompute
  13. 2026-09-18 00:08 UTCVendor advisory
  14. 2026-09-17 11:33 UTCVendor advisory
  15. 2026-09-16 23:36 UTCEG score recompute
  16. 2026-09-16 23:36 UTCVendor advisory
  17. 2026-09-16 14:08 UTCEPSS rescore
  18. 2026-09-16 11:40 UTCEG score recompute
  19. 2026-09-16 11:40 UTCVendor advisory
  20. 2026-09-16 05:15 UTCEPSS rescore
  21. 2026-09-15 23:41 UTCVendor advisory
  22. 2026-09-15 11:45 UTCEG score recompute
  23. 2026-09-15 11:45 UTCVendor advisory
  24. 2026-09-14 23:49 UTCVendor advisory
  25. 2026-09-14 11:07 UTCVendor advisory
Show 75 more
  1. 2026-09-13 23:11 UTCEG score recompute
  2. 2026-09-13 23:11 UTCVendor advisory
  3. 2026-09-13 11:16 UTCVendor advisory
  4. 2026-09-12 23:20 UTCEG score recompute
  5. 2026-09-12 23:20 UTCVendor advisory
  6. 2026-09-12 11:24 UTCVendor advisory
  7. 2026-09-11 23:28 UTCEG score recompute
  8. 2026-09-11 23:28 UTCVendor advisory
  9. 2026-09-11 14:53 UTCEPSS rescore
  10. 2026-09-11 11:02 UTCEG score recompute
  11. 2026-09-11 11:02 UTCVendor advisory
  12. 2026-09-11 09:37 UTCEPSS rescore
  13. 2026-09-10 22:25 UTCVendor advisory
  14. 2026-09-10 10:30 UTCEG score recompute
  15. 2026-09-10 10:30 UTCVendor advisory
  16. 2026-09-09 22:34 UTCVendor advisory
  17. 2026-09-09 14:24 UTCVendor advisory
  18. 2026-09-09 01:56 UTCEG score recompute
  19. 2026-09-09 01:56 UTCVendor advisory
  20. 2026-09-08 22:01 UTCEPSS rescore
  21. 2026-09-07 21:02 UTCEG score recompute
  22. 2026-09-07 21:02 UTCVendor advisory
  23. 2026-09-07 16:01 UTCEPSS rescore
  24. 2026-09-07 09:07 UTCVendor advisory
  25. 2026-09-06 20:51 UTCEG score recompute
  26. 2026-09-06 20:51 UTCVendor advisory
  27. 2026-09-06 13:47 UTCEPSS rescore
  28. 2026-09-06 08:55 UTCVendor advisory
  29. 2026-09-05 20:59 UTCEG score recompute
  30. 2026-09-05 20:59 UTCVendor advisory
  31. 2026-09-05 15:31 UTCEPSS rescore
  32. 2026-09-05 09:03 UTCVendor advisory
  33. 2026-09-04 21:07 UTCEG score recompute
  34. 2026-09-04 21:07 UTCVendor advisory
  35. 2026-09-04 09:00 UTCEG score recompute
  36. 2026-09-04 09:00 UTCVendor advisory
  37. 2026-09-04 05:07 UTCEPSS rescore
  38. 2026-09-03 21:02 UTCVendor advisory
  39. 2026-09-03 09:06 UTCVendor advisory
  40. 2026-09-02 21:09 UTCEG score recompute
  41. 2026-09-02 21:09 UTCVendor advisory
  42. 2026-09-02 14:12 UTCEPSS rescore
  43. 2026-09-02 07:50 UTCVendor advisory
  44. 2026-09-01 19:54 UTCEG score recompute
  45. 2026-09-01 19:54 UTCVendor advisory
  46. 2026-09-01 13:54 UTCEPSS rescore
  47. 2026-09-01 07:37 UTCEG score recompute
  48. 2026-09-01 07:37 UTCVendor advisory
  49. 2026-09-01 04:40 UTCEPSS rescore
  50. 2026-08-31 19:37 UTCVendor advisory
  51. 2026-08-31 07:19 UTCVendor advisory
  52. 2026-08-30 19:18 UTCEG score recompute
  53. 2026-08-30 19:18 UTCVendor advisory
  54. 2026-08-30 19:17 UTCEPSS rescore
  55. 2026-08-30 07:23 UTCEG score recompute
  56. 2026-08-30 07:23 UTCVendor advisory
  57. 2026-08-30 01:22 UTCEPSS rescore
  58. 2026-08-29 19:24 UTCVendor advisory
  59. 2026-08-29 07:28 UTCEG score recompute
  60. 2026-08-29 07:28 UTCVendor advisory
  61. 2026-08-28 21:42 UTCEPSS rescore
  62. 2026-08-28 19:27 UTCVendor advisory
  63. 2026-08-28 07:21 UTCVendor advisory
  64. 2026-08-27 19:24 UTCEG score recompute
  65. 2026-08-27 14:25 UTCEPSS rescore
  66. 2026-08-26 19:31 UTCEG score recompute
  67. 2026-08-26 14:46 UTCEPSS rescore
  68. 2026-08-25 19:39 UTCEG score recompute
  69. 2026-08-25 13:49 UTCEPSS rescore
  70. 2026-08-24 19:47 UTCEG score recompute
  71. 2026-08-23 08:00 UTCEG score recompute
  72. 2026-08-23 00:19 UTCEPSS rescore
  73. 2026-08-22 08:08 UTCEG score recompute
  74. 2026-08-21 23:49 UTCEPSS rescore
  75. 2026-08-20 20:20 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-63495?
CVE-2026-63495 is a high vulnerability published on August 20, 2026. Libevent is an event notification library. From 2.2.0-alpha-dev until 2.2.2-alpha, the libevent WebSocket server in ws.c accumulates fragmented frames in evws->incompleteframes without enforcing a total message-size limit. An unauthenticated remote client can repeatedly send fragmented WebSocket…
When was CVE-2026-63495 disclosed?
CVE-2026-63495 was first published in the National Vulnerability Database on August 20, 2026, with the most recent update on September 9, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-63495 actively exploited?
CVE-2026-63495 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 57.0% of all scored CVEs.
What is the CVSS score of CVE-2026-63495?
CVE-2026-63495 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-63495?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-63495, 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.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-63495

Explore →

Is Your Infrastructure Affected by CVE-2026-63495?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs