CVE-2026-40211

Name	CVE-2026-40211
Description	An attacker can send crafted DNS over HTTP/3 queries, triggering an exception that prevents some buffer from being freed right away. The buffer will be freed at the end of the QUIC connection, but on some setups it might be possible to open enough concurrent DoH3 streams to trigger an out-of-memory condition, resulting in a denial of service.
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)
References	DSA-6367-1

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
dnsdist (PTS)	bullseye	1.5.1-3	vulnerable
	bookworm	1.7.3-2	vulnerable
	trixie (security), trixie	1.9.15-0+deb13u1	fixed
	forky, sid	2.1.0-2	fixed

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

Package	Type	Release	Fixed Version	Urgency	Origin
dnsdist	source	bullseye	(unfixed)	end-of-life
dnsdist	source	bookworm	(unfixed)	end-of-life
dnsdist	source	trixie	1.9.15-0+deb13u1		DSA-6367-1
dnsdist	source	(unstable)	2.1.0-1

Notes

[bookworm] - dnsdist <end-of-life> (See #1119290)
[bullseye] - dnsdist <end-of-life> (see #1119290)
https://www.dnsdist.org/security-advisories/powerdns-advisory-for-dnsdist-2026-09.html#cve-2026-40211-denial-of-service-via-crafted-doh3-queries