CVE-2026-18727

A flaw was found in open-iscsi's iscsiuio component. This vulnerability involves an integer underflow and out-of-bounds read during Dynamic Host Configuration Protocol for IPv6 (DHCPv6) packet parsing. Specifically, crafted DHCPv6 Advertise traffic with a short User Datagram Protocol (UDP) length can cause the DHCPv6 payload length to underflow. An unauthenticated attacker on an adjacent network segment can exploit this by sending specially crafted IPv6 UDP traffic while the client is in an active DHCPv6 exchange, leading to a denial of service due to a process crash or service disruption.

This Moderate flaw in iscsi-initiator-utils can lead to an adjacent-network denial of service in the iscsiuio DHCPv6 client path. Exploitation requires an attacker on the same L2 segment to send crafted DHCPv6 Advertise traffic while the client is in an active DHCPv6 exchange, limiting its broader impact.

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.

If DHCPv6 is not required for iscsiuio, disable DHCPv6 handling for the relevant network interface. If DHCPv6 is necessary, restrict network exposure to trusted adjacent networks and implement firewall rules to prevent forged DHCPv6 server traffic from reaching clients on shared L2 segments. A system restart or service reload may be required for changes to take effect.