CVE-2026-5946 Invalid handling of CLASS != IN
Attackers can cause denial of service in BIND by sending crafted DNS messages with non-IN classes, triggering assertion failures in the named daemon.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-5946?
CVE-2026-5946 is a high-severity denial of service vulnerability in Isc Bind, published on 20 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Multiple flaws have been identified in `named` related to the handling of DNS messages whose CLASS is not Internet (`IN`) — for example, `CHAOS` or `HESIOD`, or DNS messages that specify meta-classes (`ANY` or `NONE`) in the question section. Specially crafted requests reaching the affected code paths — recursion, dynamic updates (`UPDATE`), zone change notifications (`NOTIFY`), or processing of `IN`-specific record types in non-`IN` data — can cause assertion failures in `named`. This issue affects BIND 9 versions 9.11.0 through 9.16.50, 9.18.0 through 9.18.48, 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, 9.11.3-S1 through 9.16.50-S1, 9.18.11-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.
Weakness: CWE-1287, CWE-843, CWE-754, CWE-617, CWE-20, CWE-125
Which versions are affected by CVE-2026-5946?
It affects 1 product.
Products include Isc Bind.
How do I fix CVE-2026-5946?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-5946 being exploited?
There is no known exploitation of CVE-2026-5946 in the wild and no public exploit code.
Other vulnerabilities in Isc Bind
Sources
Also known as ALPINE-CVE-2026-5946, AZL-87096, BELL-CVE-2026-5946, CLSA-2026-1780068979, CLSA-2026-1780476189, CLSA-2026-1780508058 and 6 more.