CVE-2026-41637 Affecting unbound package, versions <1.25.2-160000.1.1


Severity

Recommended
medium

Based on SUSE Linux Enterprise Server security rating.

Threat Intelligence

EPSS
0.37% (28th percentile)

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  • Snyk IDSNYK-SLES1600-UNBOUND-19289697
  • published27 Aug 2026
  • disclosed10 Aug 2026

Introduced: 10 Aug 2026

CVE-2026-41637  (opens in a new tab)

How to fix?

Upgrade SLES:16.0.0 unbound to version 1.25.2-160000.1.1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream unbound package and not the unbound package as distributed by SLES. See How to fix? for SLES:16.0.0 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1