CVE-2026-63384

Libevent: `evtag_unmarshal_header()` decodes a wire `uint32` length into a signed `int` return value.

Published Aug 20, 2026 CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed
Description
Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has an incorrect integer conversion in event_tagging.c when evtag_unmarshal_header uses evtag_decode_int to decode an attacker-controlled uint32 payload length and returns it as a signed int. Values above INT_MAX become negative or truncated, and evtag_unmarshal_string can use the converted value in allocation sizing, producing a wrapped large allocation request and denial of service. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4786-1 libevent security update
Debian DSA Debian DSA DSA-6493-1 libevent security update
Ubuntu USN Ubuntu USN USN-8710-1 libevent vulnerabilities
History
Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Important

Type Values Removed Values Added
First Time appeared Libevent Project
Libevent Project libevent
Vendors & Products Libevent Project
Libevent Project libevent
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has an incorrect integer conversion in event_tagging.c when evtag_unmarshal_header uses evtag_decode_int to decode an attacker-controlled uint32 payload length and returns it as a signed int. Values above INT_MAX become negative or truncated, and evtag_unmarshal_string can use the converted value in allocation sizing, producing a wrapped large allocation request and denial of service. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.
Title Libevent: `evtag_unmarshal_header()` decodes a wire `uint32` length into a signed `int` return value.
Weaknesses CWE-190
References
Metrics cvssV4_0

{'score': 8.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Aug 20, 2026, 7:50 PM
Reserved
Jul 16, 2026, 5:39 PM
Status
Awaiting Analysis
Published
Aug 20, 2026, 6:16 PM
Modified
Oct 26, 2026, 10:10 AM
Severity
Important
Public date
Aug 20, 2026, 5:53 PM