CVE-2026-32665 Affecting libunbound8 package, versions <1.25.2-160000.1.1


Severity

Recommended
0.0
high
0
10

Based on SUSE Linux Enterprise Server security rating.

Threat Intelligence

EPSS
0.47% (39th percentile)

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  • Snyk IDSNYK-SLES1600-LIBUNBOUND8-19288080
  • published27 Aug 2026
  • disclosed10 Aug 2026

Introduced: 10 Aug 2026

CVE-2026-32665  (opens in a new tab)

How to fix?

Upgrade SLES:16.0.0 libunbound8 to version 1.25.2-160000.1.1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream libunbound8 package and not the libunbound8 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, when downstream DNS-over-QUIC (DoQ) is enabled, the first two bidirectional streams on a new QUIC connection (stream_id 0 and 4) bypass the per-stream 'quic-size' gate entirely, and large input buffers are allocated later, after only the 2-byte length prefix has been received from the initial streams. As a result, a remote client can make Unbound exceed the configured 'quic-size' limit with low-cost input. Using only one connection and two streams, each sending a declared 65535-byte length prefix and then holding the streams open, a client can already trivially make Unbound roughly allocate double that amount. This is a remote availability issue / memory-accounting bypass in the downstream DoQ implementation that leads to denial of service for new DoQ clients. This vulnerability needs Unbound to be compiled with DoQ support ('--with-libngtcp2') and the 'quic-port' to be configured for the listening interfaces.

CVSS Base Scores

version 3.1