Input validation error in Unbound - CVE-2026-50243

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Main Vulnerability Database Vulnerabilities #VU139230

Input validation error in Unbound - CVE-2026-50243

Published: July 23, 2026


Vulnerability identifier: #VU139230
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-50243
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to redirect DNSSEC-protected responses to an operator-configured IP.

The vulnerability exists due to improper input validation in the response-ip/RPZ-IP rewriting handler when processing rewritten upstream A/AAAA answers with invalid DNSSEC signatures. A remote attacker can spoof a BOGUS A/AAAA answer to redirect DNSSEC-protected responses to an operator-configured IP.

Exploitation requires Unbound to be configured with the respip module in front of the validator together with a response-ip redirect rule or an RPZ file with an RPZ-IP trigger.


Affected software

Unbound
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Micro
SUSE Package Hub 15
Basesystem Module
openSUSE Leap
openEuler
Fedora
unbound
python3-unbound
unbound-debuginfo
unbound-debugsource
unbound-devel
unbound-help
unbound-libs
unbound-anchor
unbound-utils
libunbound8
libunbound8-debuginfo
unbound-anchor-debuginfo
unbound-munin
unbound-python
unbound-python-debuginfo
libunbound-devel-mini-debuginfo
libunbound-devel-mini-debugsource
libunbound-devel-mini

How to mitigate CVE-2026-50243

Install security update from vendor's website.

Unbound - update to 1.25.2
unbound - addressed in versions 1.11.0-25, 1.13.2-25, 1.17.1-19, 1.17.1-20
python3-unbound - addressed in versions 1.11.0-25, 1.13.2-25, 1.17.1-19, 1.17.1-20
unbound-debuginfo - addressed in versions 1.11.0-25, 1.13.2-25, 1.17.1-19, 1.17.1-20
unbound-debugsource - addressed in versions 1.11.0-25, 1.13.2-25, 1.17.1-19, 1.17.1-20
unbound-devel - addressed in versions 1.11.0-25, 1.13.2-25, 1.17.1-19, 1.17.1-20
unbound-help - addressed in versions 1.11.0-25, 1.13.2-25, 1.17.1-19, 1.17.1-20
unbound-libs - addressed in versions 1.11.0-25, 1.13.2-25, 1.17.1-19, 1.17.1-20
unbound-anchor - addressed in versions 1.13.2-25, 1.17.1-19, 1.17.1-20
unbound-utils - addressed in versions 1.17.1-19, 1.17.1-20
unbound - update to 1.25.2-1.fc43
libunbound8 - addressed in versions 1.25.2-150100.10.28.1, 1.25.2-150600.23.19.1
unbound-devel - addressed in versions 1.25.2-150100.10.28.1, 1.25.2-150600.23.19.1
libunbound8-debuginfo - addressed in versions 1.25.2-150100.10.28.1, 1.25.2-150600.23.19.1
unbound-anchor - addressed in versions 1.25.2-150100.10.28.1, 1.25.2-150600.23.19.1
unbound-debugsource - addressed in versions 1.25.2-150100.10.28.1, 1.25.2-150600.23.19.1
unbound-anchor-debuginfo - addressed in versions 1.25.2-150100.10.28.1, 1.25.2-150600.23.19.1
unbound-debuginfo - addressed in versions 1.25.2-150100.10.28.1, 1.25.2-150600.23.19.1
unbound-munin - update to 1.25.2-150600.23.19.1
unbound-python - update to 1.25.2-150600.23.19.1
unbound - update to 1.25.2-150600.23.19.1
unbound-python-debuginfo - update to 1.25.2-150600.23.19.1
libunbound-devel-mini-debuginfo - update to 1.25.2-150600.23.19.1
libunbound-devel-mini-debugsource - update to 1.25.2-150600.23.19.1
libunbound-devel-mini - update to 1.25.2-150600.23.19.1

External References

Related Security Bulletins