CVE-2026-18727

Summary

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.

Affected Software

Weaknesses

• CWE-191: Integer Underflow (Wrap or Wraparound)

Workarounds

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.

References

• https://access.redhat.com/security/cve/CVE-2026-18727
• https://bugzilla.redhat.com/show_bug.cgi?id=2462956

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