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: 0.4%, top 65% 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: 0%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
0%
EPSS %ILE
35%
KEV
Not listed

Published

August 20, 2026

Last Modified

August 20, 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

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.

All Vendor Advisories

(1)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 15× in last 7d / 23× 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. 2026-08-30 01:22 UTCEPSS rescore
  2. 2026-08-29 19:24 UTCVendor advisory
  3. 2026-08-29 07:28 UTCEG score recompute
  4. 2026-08-29 07:28 UTCVendor advisory
  5. 2026-08-28 21:42 UTCEPSS rescore
  6. 2026-08-28 19:27 UTCVendor advisory
  7. 2026-08-28 07:21 UTCVendor advisory
  8. 2026-08-27 19:24 UTCEG score recompute
  9. 2026-08-27 14:25 UTCEPSS rescore
  10. 2026-08-26 19:31 UTCEG score recompute
  11. 2026-08-26 14:46 UTCEPSS rescore
  12. 2026-08-25 19:39 UTCEG score recompute
  13. 2026-08-25 13:49 UTCEPSS rescore
  14. 2026-08-24 19:47 UTCEG score recompute
  15. 2026-08-23 08:00 UTCEG score recompute
  16. 2026-08-23 00:19 UTCEPSS rescore
  17. 2026-08-22 08:08 UTCEG score recompute
  18. 2026-08-21 23:49 UTCEPSS rescore
  19. 2026-08-20 20:20 UTCEG score recompute
  20. 2026-08-20 19:22 UTCEG score recompute
  21. 2026-08-20 18:17 UTCEG score recompute
  22. 2026-08-20 17:57 UTCEG score recompute
  23. 2026-08-20 17:56 UTCMITRE cvelistV5first tracked

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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. 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 0% probability of exploitation in the next 30 days, which ranks it in the top 64.6% 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

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