Vulnerability · Published Jun 25, 2026 · Assigned by OX
CVE-2026-40209Denial of service via IXFR queries
Medium 5.3
In plain English
A medium-severity security flaw in DNSdist from PowerDNS. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 53% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
An attacker might be able to cause outgoing TCP connections to backend to be stuck until a timeout occurs instead of being released immediately, by sending IXFR queries. This could be used to cause a denial of service if there is a limit to the number of concurrent connections to this backend, or if the process runs out of file descriptors.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | dnsdist | no fix listed | DEBIAN-CVE-2026-40209 |
| Debian:13 | dnsdist | 1.9.15-0+deb13u1 | DEBIAN-CVE-2026-40209 |
| Debian:14 | dnsdist | 2.1.0-1 | DEBIAN-CVE-2026-40209 |
| Ubuntu:25.10 | dnsdist | no fix listed | UBUNTU-CVE-2026-40209 |
| Ubuntu:26.04:LTS | dnsdist | no fix listed | UBUNTU-CVE-2026-40209 |
| Ubuntu:26.10 | dnsdist | no fix listed | UBUNTU-CVE-2026-40209 |
Affected products (as reported)
Weakness: CWE-772 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L