Is CVE-2026-40209 in the CISA KEV catalog?

No. CVE-2026-40209 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-40209?

CVE-2026-40209 has a CVSS v3 base score of 5.3 (MEDIUM).

What is the EPSS score for CVE-2026-40209?

CVE-2026-40209 has an EPSS score of 0.40% (32th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-40209?

Upgrade dnsdist on debian 13 to 1.9.15-0+deb13u1 or later.

CVE & CISA-KEV Catalog

CVE-2026-40209

MEDIUM

5.3

CVSS v3

NVD

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.

CWE-772

How to fix

Remediation Available

dnsdistDebian

Fixed in:1.9.15-0+deb13u1CVE-2026-40209

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityLow

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Exploit Intelligence

0.40%probability of exploitation in 30 days

32ndpercentile

Low risk: more likely to be exploited than 32% of all known CVEs.

References

Other references1

dnsdist.org

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-06-25.