CVE-2026-19666 Use-after-free in query_addnoqnameproof() via the DNS64 filter64 path
A use-after-free in BIND's DNS64 filter allows remote attackers to crash the named process via malformed DNS responses.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-19666?
CVE-2026-19666 is a high-severity use after free vulnerability in ISC BIND 9, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
On a resolver configured to use ``dns64``, if an applicable answer from the authoritative server is malformed in a specific way, the resolver `named` process will exit unexpectedly. This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1.
Weakness: CWE-416
Which versions are affected by CVE-2026-19666?
How do I fix CVE-2026-19666?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-19666 being exploited?
There is no known exploitation of CVE-2026-19666 in the wild and no public exploit code.
Sources
Also known as ALPINE-CVE-2026-19666, AZL-103365, BELL-CVE-2026-19666, CLSA-2026-1790075993, CLSA-2026-1790152508, DEBIAN-CVE-2026-19666 and 6 more.