---
id: CVE-2026-18727
title: 'Open-iscsi: open-iscsi: integer underflow in iscsiuio dhcpv6 parsing'
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 Advert…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cvssSource: cna
cwe:
  - CWE-191
vendor: Red Hat
product: iscsi-initiator-utils
affected:
  - iscsi-initiator-utils (all versions)
  - iscsi-initiator-utils (all versions)
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-08-13T19:21:57.942926Z'
published: '2026-08-12'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T19:25:52.195Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-18727'
references:
  - url: 'https://access.redhat.com/security/cve/CVE-2026-18727'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2462956'
    label: RHBZ#2462956
tags:
  - cve.org
epss: 0.00285
epssPercentile: 0.21118
ingestedAt: '2026-11-05T22:38:31.543Z'
---

## Overview

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

- `iscsi-initiator-utils (all versions)`
- `iscsi-initiator-utils (all versions)`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

### 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.