CVE-2026-41292

A flaw was found in Unbound. A remote attacker can exploit this vulnerability by sending queries with an excessive number of EDNS (Extension Mechanisms for DNS) options. This can cause Unbound threads to be held hostage while parsing and creating internal data structures for these options. Coordinated attacks can lead to resource exhaustion, resulting in a degradation of service or a denial of service (DoS) for legitimate users.

A flaw of Important severity was found in Unbound, the validating recursive DNS resolver shipped in Red Hat Enterprise Linux and included in other Red Hat products such as Red Hat OpenShift Container Platform and Red Hat In-Vehicle OS. A remote attacker requiring no privileges or user interaction can send DNS queries containing an excessive number of EDNS (Extension Mechanisms for DNS) options, which can hold Unbound worker threads hostage while they parse the options and create internal data structures for them. Coordinated attacks of this kind can exhaust server resources, resulting in degradation of service or denial of service for legitimate users; confidentiality and integrity are not affected. The Red Hat severity of Important (CVSS:3.1 score of 7.5, AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) is consistent with the NIST and upstream CVSS:3.1 scores, although the upstream CVSS:4.0 base score is lower (6.6, Moderate). Only product streams that ship the affected unbound component are impacted; several streams have been assessed as not affected in current triage. Fixes for the affected streams are being pursued by the responsible component maintainers.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.

Until patched, restrict the resolver to authorized client networks via firewall and apply DNS rate limiting per source IP. Service watchdog and cgroup limits provide resilience but are not a substitute for patching.