CVE-2026-63388

HIGHPre-NVD 8.48.4—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.4 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.1%, top 96% 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
8.4EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 8.4Exploit: 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 heap out-of-bounds write in bufferevent_sock.c when bufferevent_socket_set_conn_address_ copies a kernel-supplied AF_UNIX peer address into bufferevent_private.conn_address. Release builds compiled with NDEBUG disable the EVUTIL_ASSERT length guard, and the evhttp accept path can pass a 110-byte sockaddr from accept() into the 28-byte field. An unauthenticated local peer able to connect to an AF_UNIX listener can overwrite the adjacent dns_request pointer and heap data, causing memory corruption with confidentiality, integrity, and availability impact. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

CVSS v3
8.4
EG Score
8.4(medium)
EG Risk
38(Track)
EG Risk 38/100SSVC: 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
Severity84% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
4%
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 ef38f926e9cd (libevent/libevent)

Patch available: libevent/libevent release-2.1.13-stable (contains commit ef38f926e9cd)

https://github.com/libevent/libevent/commit/ef38f926e9cd1f082416c6fff13587bc1f431d72
github_commit Patch Available

commit 52057cb33d0c (libevent/libevent)

Patch available: libevent/libevent release-2.2.2-alpha (contains commit 52057cb33d0c)

https://github.com/libevent/libevent/commit/52057cb33d0c20c0a0453fbabe6c0c96854931b9
github Patch Available🟡 PoC Available

Heap out-of-bounds write in bufferevent_socket_set_conn_address_ reachable via AF_UNIX accept · Advisory · libevent/libevent · GitHub

https://github.com/libevent/libevent/security/advisories/GHSA-cvq5-vrvr-j338

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 13× in last 7d / 13× 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 14:46 UTCEPSS rescore
  2. 2026-08-25 16:17 UTCEG score recompute
  3. 2026-08-25 13:49 UTCEPSS rescore
  4. 2026-08-24 17:49 UTCEG score recompute
  5. 2026-08-23 08:08 UTCEG score recompute
  6. 2026-08-23 00:19 UTCEPSS rescore
  7. 2026-08-22 09:40 UTCEG score recompute
  8. 2026-08-21 23:49 UTCEPSS rescore
  9. 2026-08-21 22:26 UTCEG score recompute
  10. 2026-08-21 22:00 UTCEG score recompute
  11. 2026-08-20 18:17 UTCEG score recompute
  12. 2026-08-20 17:57 UTCEG score recompute
  13. 2026-08-20 17:56 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-63388?
CVE-2026-63388 is a high 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 heap out-of-bounds write in buffereventsock.c when buffereventsocketsetconnaddress copies a kernel-supplied AFUNIX peer address into buffereventprivate.connaddress. Release builds compiled with NDEBUG disable…
When was CVE-2026-63388 disclosed?
CVE-2026-63388 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-2026-63388 actively exploited?
CVE-2026-63388 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 96.3% of all scored CVEs.
What is the CVSS score of CVE-2026-63388?
CVE-2026-63388 has a CVSS v3 base score of 8.4 (NVD).
How do I remediate CVE-2026-63388?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-63388, 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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