Medium [CVE-2026-18727] Integer underflow in iscsiuio DHCPv6 parsing
This medium-severity Red Hat Linux advisory covers CVE-2026-18727 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat package: iscsi-initiator-utils.
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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.
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.
Red Hat severity: Moderate — CVSS 6.5 (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H). Weakness: CWE-191.
Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 9. Red Hat does not currently list a fixing RHSA for this CVE.
Affected products named by the advisory: Red Hat package: iscsi-initiator-utils.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Mitigation checklist
- 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.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
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