CVE-2026-63381: libevent Use of Uninitialized Resource
Vulnerability summary
CVE-2026-63381 is a medium (CVSS 5.8) Use of Uninitialized Resource vulnerability in libevent. EPSS estimates a 0.16% chance of exploitation in the next 30 days, higher than 4.8% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 5 · Related 1Timeline
- 20-08-2026PublishedVulnerability first disclosed.
- 21-08-2026Last modifiedVulnerability information updated.
Description
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 metrics
4 scores · 4 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated5.8MediumCVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N
- OSV · DebianEcosystem advisory · calculated5.8MediumCVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- NVDNIST5.8MediumCVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS trend
Probability
0.16%
Chance of exploitation in the next 30 days
Percentile
5%
Versus all other CVEs
30-day change
+0.04 pp
From 0.12% on 20-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Debian1 product
- libevent< 2.1.12-stable-8+deb12u1 | < 2.1.13-stable-1~deb13u1 | < 2.1.13-stable-1
Libevent1 product
- libevent≥ 2.2.0-alpha, < 2.2.2-alpha | < 2.1.13
Ubuntu1 product
- libevent< 2.1.8-stable-4ubuntu0.1~esm1 | < 2.1.11-stable-1ubuntu0.1~esm1 | < 2.1.12-stable-1ubuntu0.1 | < 2.1.12-stable-9ubuntu2.1 | < 2.1.12-stable-10ubuntu0.1
3 vendors · 3 products
References
10 links- github.com/libevent/libevent/security/advisories/GHSA-c2pj-cg4r-88c8X Refsource CONFIRM
- github.com/libevent/libevent/releases/tag/release-2.1.13-stableX Refsource MISC
- github.com/libevent/libevent/releases/tag/release-2.2.2-alphaX Refsource MISC
