CVE-2026-80225 Possible degradation of service from continuous queries on the same TCP/DoT connection
Attackers can cause service degradation in Unbound by monopolizing worker event loops via continuous TCP/DoT queries.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-80225?
CVE-2026-80225 is a medium-severity denial of service vulnerability in Nlnetlabs Unbound, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In NLnetLabs Unbound up to and including 1.26.0, a degradation of service vulnerability is present in the TCP/DoT reading procedure where there is no limit on consecutive reads. A malicious actor that can stream and sustain a rate of distinct uncached names over the TCP/DoT connection, monopolizes a single worker's entire event loop for as long as its writes stay ahead of the drain.
Weakness: CWE-770
Which versions are affected by CVE-2026-80225?
It affects 1 product.
Products include Nlnetlabs Unbound.
How do I fix CVE-2026-80225?
Upgrade to a fixed version.
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-2026-80225 being exploited?
There is no known exploitation of CVE-2026-80225 in the wild and no public exploit code.
Other vulnerabilities in Nlnetlabs Unbound
- CVE-2026-81642 Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY
- CVE-2026-33278 Possible arbitrary code execution during DNSSEC validation
- CVE-2026-42944 Heap overflow with multiple NSID, COOKIE, PADDING EDNS options
- CVE-2026-42959 Crash during DNSSEC validation of malicious content
- CVE-2026-82717 CNAME synthesis could lead to heap corruption
Sources
Also known as AZL-101724, DEBIAN-CVE-2026-80225, ECHO-cf45-1741-d9d3, GHSA-8wrv-pfvg-j383, UBUNTU-CVE-2026-80225.