CVE-2026-81736 Remote CPU denial of service through cached SVCB/HTTPS AliasMode trees
Remote attackers can cause excessive CPU consumption in BIND resolvers by querying cached SVCB/HTTPS AliasMode trees, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-81736?
CVE-2026-81736 is a high-severity denial of service 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
If a BIND resolver has cached a tree of SVCB/HTTPS AliasMode records, and is then queried for the root of that tree, the resolver will spend disproportionate CPU time constructing the response. This issue affects BIND 9 versions 9.18.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, 9.18.11-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1.
Weakness: CWE-1050
Which versions are affected by CVE-2026-81736?
How do I fix CVE-2026-81736?
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-2026-81736 being exploited?
There is no known exploitation of CVE-2026-81736 in the wild and no public exploit code.
Sources
Also known as ALPINE-CVE-2026-81736, AZL-103362, BELL-CVE-2026-81736, DEBIAN-CVE-2026-81736, ECHO-dc53-2f42-37f2, GHSA-hjmx-qf9h-v7mw and 4 more.