Medium severity · published Jun 25, 2026
CVE-2026-40209
Denial of service via IXFR queries
5.3
CVSS
0.7%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.7% · higher than 53% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
DN
DNSdist · PowerDNS
1.9.0 before 1.9.15; 2.0.0 before 2.0.7 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-40209
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-40209
www.dnsdist.org
https://www.dnsdist.org/security-advisories/powerdns-advisory-for-dnsdist-2026-09.html
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