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CVE-2026-63387

libevent: Libevent: Off-by-one stack buffer overflow leading to denial of service or data corruption

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Severity

Important

Red Hat Product Security

8.6

CVSS 3.1

Review impact separately from score.

Published · August 21, 2026

Updated · October 30, 2026

Description

A flaw was found in Libevent, an event notification library. An off-by-one stack buffer overflow exists in the dnsname_to_labels function when processing a name-bearing DNS record. A remote attacker could send a specially crafted DNS server response, which may lead to a crash or corruption of the process, resulting in a denial of service or potential information disclosure and integrity impact.

Statement

This Important vulnerability in the libevent library's DNS parsing component can lead to a denial of service or data corruption due to an off-by-one stack buffer overflow. A remote attacker can exploit this flaw with low attack complexity by providing a specially crafted DNS server response to services utilizing libevent for DNS resolution.

CVSS score applicability

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.

CVSS / CWE

CVSS 3.1 · 8.6
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H

CWE-787 · Out-of-bounds Write