CVE-2026-40211 — MEDIUM (5.3)

Vulnerability 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.

CVSS Score

5.3

MEDIUM

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

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality

NONE

Integrity

NONE

Availability

LOW

Related Weaknesses (CWE)

CWE-770

References

https://www.dnsdist.org/security-advisories/powerdns-advisory-for-dnsdist-2026-0

FAQ

What is CVE-2026-40211?

CVE-2026-40211 is a vulnerability with a CVSS score of 5.3 (MEDIUM). 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 ...

How severe is CVE-2026-40211?

CVE-2026-40211 has been rated MEDIUM with a CVSS base score of 5.3/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-40211?

Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.