CVE-2026-50251
CVE-2026-50251: 1 tracked advisory record across Red Hat. Compare source-reported impact, fixes and remediation.
Compare the source-linked records below. Ratings and product/version details belong to each advisory; they are not a single CVE-wide score or proof that every listed product is affected. How VulniPulse collects and checks evidence.
Vendor advisory comparison
Red Hat
1 advisory- Advisory severityMedium5.3
Medium [CVE-2026-50251] Denial of Service via crafted DNS glue records
CVE-2026-50251Source published Source updated
In NLnet Labs Unbound up to and including version 1.25.1, when 'unwanted-reply-threshold' is enabled (set to any value greater than zero), glue records of 0.0.0.0/::0 can short-circuit Unbound, on systems that can direct such traffic, by issuing DNS queries and receiving seemingly unwanted replies since the remote IP does not match the original source IP of 0.0.0.0/::0. This behavior keeps on looping for the glue records and pushing the counter to the configured 'unwanted-reply-threshold' that triggers a defensive cache clear. A malicious actor who controls a delegation that returns in-bailiwick glue of 0.0.0.0/::0 can drive the counter to the limit of 'unwanted-reply-threshold' to the threshold and trigger a cache clean of the message and rrset caches; at will, indefinitely, without…
- Affected products in this advisory
- Red Hat Hardened Images
- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
4 more entries in the full advisory.
- Source-reported affected versions
- 1.25.1
- Source-reported fixed versions
- unbound-main-1.25.2-0.1.hum1
- RHSA-2026:43588
- Mitigation guidance
- To mitigate this issue, configure Unbound to disable the `unwanted-reply-threshold` option by setting it to `0` in the `unbound.conf` file. This prevents the cache clearing behavior triggered by malicious glue records. After modifying the configuration, restart the Unbound service for the changes to take effect.
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