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8.7 High

CVE-2026-42959 NLnet Labs Unbound up to and including version 1.25.0 has a denial of service vulnerability in the DNSSEC validator that…

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 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.

Affected products and versions

Product Affected versions Fixed in
unbound 1.25 earliest → < 1.25.1 1.25.1
Red Hat Enterprise Linux AppStream (v. 10) Versions not published
Red Hat Enterprise Linux AppStream (v. 8) Versions not published
Red Hat Enterprise Linux AppStream (v. 9) Versions not published
Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) Versions not published
Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) Versions not published
Red Hat Hardened Images 1.25 earliest → < 1.25.1-0.1.hum1 1.25.1-0.1.hum1
Red Hat Enterprise Linux 6 Versions not published
Red Hat Enterprise Linux 7 Versions not published
Show the 4 other branches
Product Affected versions Fixed in
Red Hat OpenShift Container Platform 4 Versions not published
Red Hat Enterprise Linux 10 Versions not published
Red Hat Enterprise Linux 8 Versions not published
Red Hat Enterprise Linux 9 Versions not published

References

Timeline

  1. Published
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Other CVEs of unbound

The 58 CVEs of unbound →
CVE-2026-97206 NLnet Labs Unbound, 1.22.0 up to and including version 1.26.1, contains a DNS-over-QUIC (DoQ) lifetime bug reachable… 7.5 High CVE-2026-96405 NLnet Labs Unbound up to and including version 1.26.1 limits compression-pointer traversal for each individual… 5.3 Medium CVE-2026-50106 When NLnet Labs Unbound up to and including version 1.26.1 is configured with both a root trust anchor and an additional… 6.5 Medium CVE-2026-35501 When NLnet Labs Unbound 1.0.1 up to and including version 1.26.1 is configured with both a root trust anchor and an… 3.7 Low
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