CVE-2026-42534 Affecting unbound-devel package, versions <1.20.0-150600.23.16.1


Severity

Recommended
0.0
medium
0
10

Based on SUSE Linux Enterprise Server security rating.

Threat Intelligence

EPSS
0.52% (41st percentile)

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  • Snyk IDSNYK-SLES156-UNBOUNDDEVEL-17217848
  • published6 Jun 2026
  • disclosed5 Jun 2026

Introduced: 5 Jun 2026

NewCVE-2026-42534  (opens in a new tab)

How to fix?

Upgrade SLES:15.6 unbound-devel to version 1.20.0-150600.23.16.1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream unbound-devel package and not the unbound-devel package as distributed by SLES. See How to fix? for SLES:15.6 relevant fixed versions and status.

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the jostle logic that could defeat its purpose and degrade resolution performance. Retransmits of the same query could renew the age of slow running queries and not allow the jostle logic to see them as aged and potential targets for replacement with new queries. An adversary who can query a vulnerable Unbound and who can control a domain name server that replies slowly and/or maliciously to Unbound's queries can exploit the vulnerability and degrade the resolution performance of Unbound. When Unbound's 'num-queries-per-thread' reaches its limit, the jostle logic kicks in. When a new query comes in, half of the available queries that are also slow to resolve are candidates for replacement. The vulnerability then happens because duplicate queries that need resolution would skew the aging result by using the timestamp of the latest duplicate query instead of the original one that started the resolution effort. Cache and local data response performance remains unaffected. Coordinated attacks could raise this to a denial of resolution service. Unbound 1.25.1 contains a patch with a fix to attach an initial, non-updatable start time for incoming queries that allow the jostle logic to work as intended.

CVSS Base Scores

version 3.1