CVE-2026-63383: libevent Out-of-bounds Read
Vulnerability summary
CVE-2026-63383 is a high (CVSS 8.7) Out-of-bounds Read vulnerability in libevent. EPSS estimates a 0.49% chance of exploitation in the next 30 days, higher than 40.7% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 6 · Related 1Timeline
- 20-08-2026PublishedVulnerability first disclosed.
- 20-08-2026Last modifiedVulnerability information updated.
Description
Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent can read beyond a contiguous evbuffer region in event_tagging.c when decode_tag_internal requests at most five bytes from evbuffer_pullup but iterates using the full logical buffer length. A fragmented evbuffer containing a six-byte malformed tag can therefore advance past the pullup window and trigger an out-of-bounds read, which can crash a process that decodes attacker-controlled tagged RPC data. 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 · calculated8.7HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- OSV · DebianEcosystem advisory · calculated8.7HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/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
- NVDNIST8.7HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/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
0.49%
Chance of exploitation in the next 30 days
Percentile
41%
Versus all other CVEs
30-day change
+0.10 pp
From 0.38% 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< 2.0.21-stable-1ubuntu1.14.04.2+esm1 | < 2.0.21-stable-2ubuntu0.16.04.1+esm1 | < 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-fj29-64w6-73h6X 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
