CVE-2026-63387

Name	CVE-2026-63387
Description	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.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
libevent (PTS)	bullseye	2.1.12-stable-1	vulnerable
	bookworm	2.1.12-stable-8	vulnerable
	trixie	2.1.12-stable-10	vulnerable
	forky, sid	2.1.13-stable-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
libevent	source	(unstable)	2.1.13-stable-1

Notes

https://github.com/libevent/libevent/security/advisories/GHSA-58rx-7448-jw47
Fixed by: https://github.com/libevent/libevent/commit/377b9022c3ac61aa4540b5dc4b70c60bf74c663d (release-2.1.13-stable)
Fixed by: https://github.com/libevent/libevent/commit/9877a7205ea024d0120effb040e1b8e034435407 (release-2.2.2-alpha)