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 — 3 sources updated 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

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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

August 21, 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

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 12× in last 7d / 12× 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. 2026-08-26 20:11 UTCEG score recompute
  2. 2026-08-26 14:46 UTCEPSS rescore
  3. 2026-08-25 20:37 UTCEG score recompute
  4. 2026-08-25 13:49 UTCEPSS rescore
  5. 2026-08-24 21:02 UTCEG score recompute
  6. 2026-08-22 21:58 UTCEG score recompute
  7. 2026-08-21 23:49 UTCEPSS rescore
  8. 2026-08-21 22:26 UTCEG score recompute
  9. 2026-08-21 21:53 UTCEG score recompute
  10. 2026-08-20 18:17 UTCEG score recompute
  11. 2026-08-20 17:57 UTCEG score recompute
  12. 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 August 21, 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 97.9% 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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