CVE-2026-44687 Affecting libunbound8 package, versions <1.25.2-160000.1.1


Severity

Recommended
medium

Based on SUSE Linux Enterprise Server security rating.

Threat Intelligence

EPSS
0.22% (12th percentile)

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  • Snyk IDSNYK-SLES1600-LIBUNBOUND8-19287844
  • published27 Aug 2026
  • disclosed10 Aug 2026

Introduced: 10 Aug 2026

CVE-2026-44687  (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 1.13.2 up to and including 1.25.1, stub or forward zones where the name is below an intermediate labed below a DNSSEC signed zone could be shadowed by the intermediate label's secure NXDOMAIN answer from the parent. This is caused by an off-by-one error in 'harden-below-nxdomain' logic; enabled by default. It effectively bypasses the configuration and the configured stub/forward zone is never contacted. 'harden-below-nxdomain' does an upward DNS cache walk together with a delegation point guard that does not allow NXDOMAIN synthesis above stub/forward zones. The guard tests the domain name but before stripping a label. This results in an iteration where the domain name equals the configured stub/forward zone apex that passes the guard, strips one more label, and probes the cache at the apex's immediate public parent. If that parent has a cached DNSSEC-secure NXDOMAIN, which it will for any private namespace nested two or more labels under a signed public name, the walk returns it and the configured stub/forward upstream is never contacted. This can only be triggered by the query for the intermediate label (between the stub/forward apex and the DNSSEC parent zone).

CVSS Base Scores

version 3.1