Cyber Posture

CVE-2026-42959

High
Microsoft: not affectedMSmacOS: not affectedMacLinux: not affectedLnxMobile: not affectedMobNetwork: not affectedNetApplication: affectedAppOther: not affectedOth

Published: 20 May 2026

Published
20 May 2026
Modified
20 May 2026
KEV Added
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Patch
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CVSS Score 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS Score 0.0004 12.8th percentile
Risk Priority 15 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-42959 is a high-severity Access of Uninitialized Pointer (CWE-824) vulnerability in Nlnetlabs Unbound. Its CVSS base score is 7.5 (High).

Operationally, ranked at the 12.8th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

NVD Description

NLnet Labs Unbound up to and including version 1.25.0 has a denial of service vulnerability in the DNSSEC validator that can lead to a crash given malicious upstream replies. When Unbound constructs chase-reply messages for validation, the code uses the…

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wrong counter to calculate write offsets for ADDITIONAL section rrsets. DNAME duplication could increase the ANSWER section count and authority filtering could decrease the AUTHORITY section count and create an uninitialized array slot. Combining these two, the validator later dereferences this uninitialized pointer, causing an immediate process crash. An adversary controlling a DNSSEC-signed domain can trigger this bug with a single query by configuring a DNAME chain with unsigned CNAMEs and a response containing unsigned AUTHORITY records alongside signed ADDITIONAL glue records. Unbound 1.25.1 contains a patch with a fix to use the proper counters to calculate the write offsets.

Deeper analysisAI

Automated synthesis unavailable for this CVE.

Details

CWE(s)
CWE-824

Affected Products

nlnetlabs
unbound
≤ 1.25.1

EU & UK References

References