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Fencer Vulns
medium 5.3

CVE-2026-40211 json

Denial of service via crafted DoH3 queries

published 2026-06-25 4 mo ago modified 2026-10-25 14 d ago also EUVD-2026-39350

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 53%
public exploits
0
none known

Summary

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.

Patch / fix

  • PowerDNS DNSdist 1.9.15, 2.0.7
  • dnsdist Debian 13 1.9.15-0+deb13u1
  • dnsdist Debian 14 2.1.0-1

debian advisories DEBIAN-CVE-2026-40211

  • dnsdist SLES 16.0, SLES for SAP applications 16.0 1.9.15-160000.1.1

suse advisories SUSE-SU-2026:23123-1SUSE-SU-2026:23146-1

  • dnsdist openSUSE Leap 16.0 1.9.15-160000.1.1
  • dnsdist openSUSE Tumbleweed 2.0.7-1.1

opensuse advisories openSUSE-SU-2026:21533-1openSUSE-SU-2026:11411-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-40211 updated cvss 7.5

dnsdist: denial of service via crafted DoH3 queries

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
4 mo ago

Exploit prediction

0.70% chance of exploitation in the next 30 days, higher than 53% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected products

  • PowerDNS DNSdist

Classification

Weakness
  • CWE-770 Allocation of Resources Without Limits or Throttling

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.