CVE-2026-18726 is a vulnerability in the open-iscsi component of Red Hat Enterprise Linux 10. It allows a remote attacker on the same Layer 2 network segment to cause a denial of service by sending a crafted ICMPv6 Router Advertisement containing a zero-length option. This triggers an infinite loop in the iscsiuio daemon, resulting in sustained CPU consumption and unresponsiveness of the daemon, impacting system availability. Additionally, there is a secondary risk of out-of-bounds reads with short IPv6 payloads, though no memory corruption or data leakage has been confirmed. The vulnerability requires adjacency on the local network segment and affects IPv6-enabled interfaces handled by iscsiuio. Red Hat advisory recommends mitigation by restricting or filtering ICMPv6 Router Advertisements or disabling their processing on affected interfaces. No official patch or fix has been published yet.

The vulnerability causes a denial of service by triggering an infinite loop in the iscsiuio daemon, leading to sustained CPU usage and unresponsiveness of the daemon, which impacts system availability. There is no confirmed impact on confidentiality or integrity. The attack requires the attacker to be on the same local network segment and to send specially crafted ICMPv6 Router Advertisements. A secondary risk of out-of-bounds reads exists but no memory corruption or data exposure has been confirmed.

Red Hat advises restricting ICMPv6 Router Advertisements from untrusted sources on any network segment where iscsiuio interfaces are exposed. Alternatively, disabling IPv6 Router Advertisement processing on affected interfaces if not operationally required can mitigate the issue. This can be done by configuring firewall rules to filter ICMPv6 type 134 messages or adjusting network interface settings to prevent RA-driven IPv6 configuration. A service restart may be required for changes to take effect. No official patch or fix is currently available; patch status is not yet confirmed — check the Red Hat advisory for updates.