Is CVE-2026-40211 in the CISA KEV catalog?

No. CVE-2026-40211 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-40211?

CVE-2026-40211 has a CVSS v3 base score of 5.3 (MEDIUM).

What is the EPSS score for CVE-2026-40211?

CVE-2026-40211 has an EPSS score of 0.41% (33th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-40211?

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

CVE & CISA-KEV Catalog

CVE-2026-40211

MEDIUM

5.3

CVSS v3

NVD

Description

An attacker can send crafted DNS over HTTP/3 queries, triggering an exception that prevents some buffer from being freed right away. The buffer will be freed at the end of the QUIC connection, but on some setups it might be possible to open enough concurrent DoH3 streams to trigger an out-of-memory condition, resulting in a denial of service.

CWE-770Allocation of Resources Without Limits or Throttling

How to fix

Remediation Available

dnsdistDebian

Fixed in:1.9.15-0+deb13u1CVE-2026-40211

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

0.41%probability of exploitation in 30 days

33rdpercentile

Low risk: more likely to be exploited than 33% 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.