CVE-2026-5947

Name	CVE-2026-5947
Description	Undefined behavior may result due to a race condition leading to a use-after-free violation. If BIND receives an incoming DNS message signed with SIG(0), it begins work to validate that signature. If, during that validation, the "recursive-clients" limit is reached (as would occur during a query flood), and that same DNS message is discarded per the limit, there is a brief window of time while the SIG(0) validation may attempt to read the now-discarded DNS message. This issue affects BIND 9 versions 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, and 9.20.9-S1 through 9.20.22-S1. BIND 9 versions 9.18.28 through 9.18.49 and 9.18.28-S1 through 9.18.49-S1 are NOT affected.
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
bind9 (PTS)	bullseye	1:9.16.50-1~deb11u2	fixed
	bullseye (security)	1:9.16.50-1~deb11u5	fixed
	bookworm	1:9.18.47-1~deb12u1	fixed
	bookworm (security)	1:9.18.49-1~deb12u1	fixed
	trixie	1:9.20.21-1~deb13u1	vulnerable
	trixie (security)	1:9.20.23-1~deb13u1	fixed
	forky	1:9.20.22-1	vulnerable
	sid	1:9.20.23-1	fixed

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

Package	Type	Release	Fixed Version
bind9	source	bullseye	(not affected)
bind9	source	bookworm	(not affected)
bind9	source	trixie	1:9.20.23-1~deb13u1
bind9	source	(unstable)	1:9.20.23-1

Notes

[bookworm] - bind9 <not-affected> (Only affects Bind 9.20)
[bullseye] - bind9 <not-affected> (Only affects Bind 9.20)
https://kb.isc.org/docs/cve-2026-5947