CVE-2026-40211
Denial of service via crafted DoH3 queries
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.
INFO
Published Date :
June 25, 2026, 1:16 p.m.
Last Modified :
Oct. 25, 2026, 11:10 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | 8ce71d90-2354-404b-a86e-bec2cc4e6981 | ||||
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update the affected software to the latest version.
- Apply vendor patches for buffer handling.
- Monitor memory usage on critical systems.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-40211.
| URL | Resource |
|---|---|
| https://www.dnsdist.org/security-advisories/powerdns-advisory-for-dnsdist-2026-09.html |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-40211 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-40211
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-40211 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-40211 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Translated by [email protected]
Oct. 25, 2026
Action Type Old Value New Value Added Translation Title: DNSdist de PowerDNS, Description: Un atacante puede enviar consultas DNS sobre HTTP/3 manipuladas, lo que desencadena una excepción que impide que algún búfer se libere de inmediato. El búfer se liberará al final de la conexión QUIC, pero en algunas configuraciones podría ser posible abrir suficientes flujos DoH3 concurrentes para desencadenar una condición de falta de memoria, lo que resulta en una denegación de servicio. -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 25, 2026
Action Type Old Value New Value Added CWE CWE-770 Added SSVC {'id': 'CVE-2026-40211', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-06-25T13:44:56.582604Z'} -
New CVE Received by [email protected]
Jun. 25, 2026
Action Type Old Value New Value Added Affected [{'repo': 'https://github.com/PowerDNS/pdns', 'vendor': 'PowerDNS', 'modules': ['DNS over HTTP3'], 'product': 'DNSdist', 'versions': [{'status': 'affected', 'version': '1.9.0', 'lessThan': '1.9.15', 'versionType': 'semver'}, {'status': 'affected', 'version': '2.0.0', 'lessThan': '2.0.7', 'versionType': 'semver'}], 'packageName': 'dnsdist', 'programFiles': ['dnsdist-crypto.cc'], 'collectionURL': 'https://repo.powerdns.com/', 'defaultStatus': 'unaffected'}] Added 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L Added Reference https://www.dnsdist.org/security-advisories/powerdns-advisory-for-dnsdist-2026-09.html