CVE-2026-69186

Name	CVE-2026-69186
Description	c-ares is an asynchronous resolver library. Prior to 1.34.7, ares_dns_parse() trusts the attacker-controlled ANCOUNT, NSCOUNT, and ARCOUNT fields before confirming that the DNS response contains enough bytes for the claimed records. Because process_answer() invokes parsing before transaction ID and question validation, a malicious DNS response can cause ares_dns_record_rr_prealloc() and ares_array_set_size() to reserve disproportionate heap memory for a tiny message. Repeated responses create large allocation and release cycles that can degrade or deny name resolution, without causing memory corruption or information disclosure. This issue is fixed in version 1.34.7.
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
c-ares (PTS)	bookworm	1.18.1-3	fixed
	trixie (security), trixie	1.34.5-1+deb13u1	vulnerable
	forky, sid	1.34.8-1	fixed

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

Package	Type	Release	Fixed Version
c-ares	source	bullseye	(not affected)
c-ares	source	bookworm	(not affected)
c-ares	source	(unstable)	1.34.7-1

Notes

[trixie] - c-ares <no-dsa> (Minor issue)
[bookworm] - c-ares <not-affected> (New DNS-record parser prealloc (ares_dns_record_rr_prealloc/ares_array_set_size) not present; introduced in the 1.20+ rewrite)
[bullseye] - c-ares <not-affected> (New DNS-record parser prealloc not present; introduced in the 1.20+ rewrite)
https://www.openwall.com/lists/oss-security/2026/07/06/8
https://github.com/c-ares/c-ares/security/advisories/GHSA-jv8r-gqr9-68wj
Fixed by: https://github.com/c-ares/c-ares/commit/eaded4cb200b2a5f8d73f11021ff7c8d6968aaab (main)
Fixed by: https://github.com/c-ares/c-ares/commit/e47c203f91cd8b749c8736bc18d75a31ffdec8f4 (v1.34.7)