CVE detail
CVE-2026-42534
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.
Buzz score
Why this CVE is surfacing
This all-time snapshot uses the same composite formula as Trending across a 30-year evidence window, rather than a current rolling window.
Buzz score components · mention 19.5 · diversity 18.0 · KEV 0.0 · OTX 0.0 · PoC 0.0
Why it matters now
Mention timeline
- Total mentions
- 0
- within the 30d window
- Peak daily
- 0
- highest bucket
Evidence
Source links by recency
6 source links · newest first
Information published.
vendormsrc.microsoft.comMay 21, 2026, 8:02 AM- https://access.redhat.com/errata/RHSA-2026:24013access.redhat.com
No excerpt available.
Vendor Advisoryaccess.redhat.comMay 20, 2026, 10:16 AM - https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42534.jsonsecurity.access.redhat.com
No excerpt available.
Vendor Advisorysecurity.access.redhat.comMay 20, 2026, 10:16 AM - https://bugzilla.redhat.com/show_bug.cgi?id=2480131bugzilla.redhat.com
No excerpt available.
Exploitbugzilla.redhat.comMay 20, 2026, 10:16 AM - https://access.redhat.com/security/cve/CVE-2026-42534access.redhat.com
No excerpt available.
Vendor Advisoryaccess.redhat.comMay 20, 2026, 10:16 AM - https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42534.txtwww.nlnetlabs.nl
No excerpt available.
Vendor Advisorywww.nlnetlabs.nlMay 20, 2026, 10:16 AM
Exploit code
Public exploit repository references
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0 repository references · best confidence N/A · max 0 stars
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