CVE-2026-63381

MEDIUMPre-NVD 5.85.8—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.1%, top 98% 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 — Patch released this week
5.8EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.8Exploit: None knownExposed: 0

A fix is available — apply it.

Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has a use-after-free in buffer.c when evbuffer_add_buffer_reference processes an output buffer whose out_total_len is zero. evbuffer_free_all_chains frees the initial empty chain without resetting outbuf->first, outbuf->last, or outbuf->last_with_datap, and APPEND_CHAIN_MULTICAST subsequently dereferences the dangling chain pointer. A caller that can drive this buffer state can cause memory corruption or a process crash. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

CVSS v3
5.8
EG Score
5.8(medium)
EG Risk
26(Track)
EG Risk 26/100SSVC: Track

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
Severity58% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
2%
KEV
Not listed

Published

August 20, 2026

Last Modified

September 9, 2026

Advisory Details (5)

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_release Patch Available

Libevent 2.1.13-stable

Patch available: libevent/libevent release-2.1.13-stable

https://github.com/libevent/libevent/releases/tag/release-2.1.13-stable
github_commit Patch Available

commit 9db091b04f56 (libevent/libevent)

Patch available: libevent/libevent release-2.2.2-alpha (contains commit 9db091b04f56)

https://github.com/libevent/libevent/commit/9db091b04f569be3a700fa9860ef02f90b830af9
github_commit Patch Available

commit 5cb95ba2f804 (libevent/libevent)

Patch available: libevent/libevent release-2.1.13-stable (contains commit 5cb95ba2f804)

https://github.com/libevent/libevent/commit/5cb95ba2f804f8aff46f88d58391c71e1251cd1c
github Patch Available🟡 PoC Available

Dangling Pointer in `evbuffer_add_buffer_reference` · Advisory · libevent/libevent · GitHub

https://github.com/libevent/libevent/security/advisories/GHSA-c2pj-cg4r-88c8

Vendor Advisories for CVE-2026-63381(1)

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

Patch Availability(4)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulibevent-pthreads-2.0-5 (2.0.21-stable-1ubuntu1.14.04.2+esm1) @ trusty2026-09-18ubuntu
redhatlibevent-0:2.1.13-1.el10_22026-09-16redhat
redhatlibevent-0:2.1.13-1.el9_82026-09-16redhat
redhatlibevent-main-2.1.12-19.1.hum12026-08-29redhat

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

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFixed inDependents
libevent2.1.12-stable-10 ... 2.1.13-stable-1 (7 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
libevent2.1.12-stable-10, 2.1.13-stable-1——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
libevent2.1.12-stable-102.1.13-stable-1—

Weakness Classification(1)

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

Additional Vendor Advisories

(3)

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 16× in last 7d / 64× 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. 2026-09-18 21:39 UTCEG score recompute
  2. 2026-09-18 21:39 UTCVendor advisory
  3. 2026-09-18 19:28 UTCEPSS rescore
  4. 2026-09-17 21:19 UTCEG score recompute
  5. 2026-09-17 21:19 UTCVendor advisory
  6. 2026-09-16 20:01 UTCEG score recompute
  7. 2026-09-16 20:01 UTCVendor advisory
  8. 2026-09-16 14:08 UTCEPSS rescore
  9. 2026-09-16 05:15 UTCEPSS rescore
  10. 2026-09-15 19:52 UTCEG score recompute
  11. 2026-09-15 19:52 UTCVendor advisory
  12. 2026-09-14 20:18 UTCVendor advisory
  13. 2026-09-13 20:43 UTCEG score recompute
  14. 2026-09-13 20:43 UTCVendor advisory
  15. 2026-09-12 21:11 UTCEG score recompute
  16. 2026-09-12 21:11 UTCVendor advisory
  17. 2026-09-11 21:39 UTCEG score recompute
  18. 2026-09-11 21:39 UTCVendor advisory
  19. 2026-09-11 14:53 UTCEPSS rescore
  20. 2026-09-11 09:37 UTCEPSS rescore
  21. 2026-09-10 22:06 UTCEG score recompute
  22. 2026-09-10 22:06 UTCVendor advisory
  23. 2026-09-09 22:34 UTCVendor advisory
  24. 2026-09-09 01:56 UTCEG score recompute
  25. 2026-09-09 01:56 UTCVendor advisory
Show 42 more
  1. 2026-09-08 22:01 UTCEPSS rescore
  2. 2026-09-07 19:44 UTCEG score recompute
  3. 2026-09-07 19:44 UTCVendor advisory
  4. 2026-09-07 16:01 UTCEPSS rescore
  5. 2026-09-06 20:12 UTCEG score recompute
  6. 2026-09-06 20:12 UTCVendor advisory
  7. 2026-09-06 13:47 UTCEPSS rescore
  8. 2026-09-05 20:39 UTCEG score recompute
  9. 2026-09-05 20:39 UTCVendor advisory
  10. 2026-09-05 15:31 UTCEPSS rescore
  11. 2026-09-04 21:07 UTCEG score recompute
  12. 2026-09-04 21:07 UTCVendor advisory
  13. 2026-09-03 20:41 UTCVendor advisory
  14. 2026-09-02 21:09 UTCEG score recompute
  15. 2026-09-02 21:09 UTCVendor advisory
  16. 2026-09-02 14:12 UTCEPSS rescore
  17. 2026-09-01 18:39 UTCEG score recompute
  18. 2026-09-01 18:39 UTCVendor advisory
  19. 2026-09-01 13:54 UTCEPSS rescore
  20. 2026-09-01 04:40 UTCEPSS rescore
  21. 2026-08-31 19:04 UTCEG score recompute
  22. 2026-08-31 19:04 UTCVendor advisory
  23. 2026-08-30 19:17 UTCEPSS rescore
  24. 2026-08-30 18:32 UTCEG score recompute
  25. 2026-08-30 18:32 UTCVendor advisory
  26. 2026-08-30 01:22 UTCEPSS rescore
  27. 2026-08-29 19:00 UTCEG score recompute
  28. 2026-08-28 21:42 UTCEPSS rescore
  29. 2026-08-27 19:43 UTCEG score recompute
  30. 2026-08-27 14:25 UTCEPSS rescore
  31. 2026-08-26 20:11 UTCEG score recompute
  32. 2026-08-26 14:46 UTCEPSS rescore
  33. 2026-08-25 20:37 UTCEG score recompute
  34. 2026-08-25 13:49 UTCEPSS rescore
  35. 2026-08-24 21:02 UTCEG score recompute
  36. 2026-08-22 21:58 UTCEG score recompute
  37. 2026-08-21 23:49 UTCEPSS rescore
  38. 2026-08-21 22:26 UTCEG score recompute
  39. 2026-08-21 21:53 UTCEG score recompute
  40. 2026-08-20 18:17 UTCEG score recompute
  41. 2026-08-20 17:57 UTCEG score recompute
  42. 2026-08-20 17:56 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-63381?
CVE-2026-63381 is a medium vulnerability published on August 20, 2026. Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has a use-after-free in buffer.c when evbufferaddbufferreference processes an output buffer whose outtotallen is zero. evbufferfreeallchains frees the initial empty chain without resetting outbuf->first,…
When was CVE-2026-63381 disclosed?
CVE-2026-63381 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-2026-63381 actively exploited?
CVE-2026-63381 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 97.8% of all scored CVEs.
What is the CVSS score of CVE-2026-63381?
CVE-2026-63381 has a CVSS v3 base score of 5.8 (NVD).
How do I remediate CVE-2026-63381?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-63381, 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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