Copyright © 2012 Red Hat, Inc. All rights reserved. Important 2026-08-20T17:53:41 libevent: Libevent: Off-by-one stack buffer overflow leading to denial of service or data corruption 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H CWE-787

Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has an off-by-one stack buffer overflow in evdns.c when dnsname_to_labels formats a name-bearing DNS record at the end of the 64 KB stack buffer allocated by evdns_server_request_format_response. The final-label check permits j plus label_len plus one to equal buf_len, after which the terminating null byte is written to buf[buf_len]. A crafted DNS server response containing PTR, CNAME, MX, NS, or SOA data can trigger the one-byte out-of-bounds write and crash or corrupt the process. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

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.

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. 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. Red Hat Enterprise Linux 10 2026-09-16T00:00:00Z RHSA-2026:67909 libevent-0:2.1.13-1.el10_2 Red Hat Enterprise Linux 8 2026-09-16T00:00:00Z RHSA-2026:67908 libevent-0:2.1.8-11.el8_10 Red Hat Enterprise Linux 8 2026-09-16T00:00:00Z RHSA-2026:67908 libevent-0:2.1.8-11.el8_10 Red Hat Enterprise Linux 9 2026-09-16T00:00:00Z RHSA-2026:67910 libevent-0:2.1.13-1.el9_8 Red Hat Enterprise Linux 9 2026-09-16T00:00:00Z RHSA-2026:67910 libevent-0:2.1.13-1.el9_8 Red Hat Hardened Images 2026-09-03T00:00:00Z RHSA-2026:63388 libevent-main-2.1.13-0.1.hum1 Red Hat Enterprise Linux 6 Affected libevent Red Hat Enterprise Linux 6 Will not fix libevent2 Red Hat Enterprise Linux 7 Affected libevent Red Hat OpenShift Container Platform 4 Affected openshift/ose-rhel-coreos-8 Red Hat OpenShift Container Platform 4 Affected openshift/ose-rhel-coreos-9 https://www.cve.org/CVERecord?id=CVE-2026-63387 https://nvd.nist.gov/vuln/detail/CVE-2026-63387 https://github.com/libevent/libevent/releases/tag/release-2.1.13-stable https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha https://github.com/libevent/libevent/security/advisories/GHSA-58rx-7448-jw47