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NVD Vulnerability Details :
CVE-2026-41637
Analyzed
More InfoOfficial Page
Source-sep@nlnetlabs.nl
View Known Exploited Vulnerability (KEV) details
Published At-22 Jul, 2026 | 14:17
Updated At-24 Jul, 2026 | 13:57

In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, client terminated DNS-over-QUIC (DoQ) queries are not accounted properly by Unbound resulting in low-cost inflation of the waiting number of replies for already in-flight resolution queries. This results in degradation of resolution service for new clients for already in-flight queries. A malicious actor can exploit the vulnerability by issuing DoQ queries for query names that need resolution and proceeding on immediately terminating the query by one of STOP_SENDING/RESET_STREAM/CONNECTION_CLOSE QUIC frames. Those terminated DoQ queries are not properly counted for and keep inflating the number of waiting replies for in-flight queries. When the maximum is reached, it results in silent query drops for new clients needing resolution for already in-flight queries. This vulnerability needs Unbound to be compiled with DoQ support ('--with-libngtcp2') and the 'quic-port' to be configured for the listening interfaces. Additionally, a malicious actor needs access to multiple source IPs to bypass the by-default configured 'wait-limit' option.

CISA Catalog
Date AddedDue DateVulnerability NameRequired Action
N/A
Date Added: N/A
Due Date: N/A
Vulnerability Name: N/A
Required Action: N/A
Metrics
TypeVersionBase scoreBase severityVector
Secondary3.13.7LOW
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
N/A
Type: Secondary
Version: 3.1
Base score: 3.7
Base severity: LOW
Vector:
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Type: N/A
Version:
Base score:
Base severity: N/A
Vector:
CPE Matches

nlnetlabs
nlnetlabs
>>unbound>>Versions from 1.22.0(inclusive) to 1.25.2(exclusive)
cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*
Weaknesses
CWE IDTypeSource
CWE-772Secondarysep@nlnetlabs.nl
CWE ID: CWE-772
Type: Secondary
Source: sep@nlnetlabs.nl
Evaluator Description

Evaluator Impact

Evaluator Solution

Vendor Statements

References
HyperlinkSourceResource
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-41637.txtsep@nlnetlabs.nl
Vendor Advisory
Hyperlink: https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-41637.txt
Source: sep@nlnetlabs.nl
Resource:
Vendor Advisory
Change History
0Changes found

Details not found