---
id: CVE-2026-53918
title: odhcpd DHCPv6 IA dangling first pointer use-after-free
summary: >-
  odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt.
  Prior to version 25.12, odhcpd's DHCPv6 IA handler keeps a per-message `first`
  lease pointer so multiple IA options in one message reuse the same Reconfigure
  …
severity: high
cvss: 8.8
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N'
cvssSource: cna
cwe:
  - CWE-416
  - CWE-672
  - CWE-825
vendor: openwrt
product: odhcpd
affected:
  - odhcpd < 25.12
published: '2026-10-23'
updated: '2026-10-23'
sourceUpdated: '2026-10-23T13:21:00.665Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-53918'
references:
  - url: 'https://github.com/openwrt/odhcpd/security/advisories/GHSA-44ff-jcwh-wgc2'
    label: 'https://github.com/openwrt/odhcpd/security/advisories/GHSA-44ff-jcwh-wgc2'
  - url: >-
      https://github.com/openwrt/odhcpd/commit/26b122007030ebf192376aff8f98d428b25e2a93
    label: >-
      https://github.com/openwrt/odhcpd/commit/26b122007030ebf192376aff8f98d428b25e2a93
  - url: >-
      https://github.com/openwrt/odhcpd/commit/5b283832c0a77aed20f1cc384ffc40bc768b06e9
    label: >-
      https://github.com/openwrt/odhcpd/commit/5b283832c0a77aed20f1cc384ffc40bc768b06e9
tags:
  - cve.org
ingestedAt: '2026-10-23T14:28:08.711Z'
---

## Overview

odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt. Prior to version 25.12, odhcpd's DHCPv6 IA handler keeps a per-message `first` lease pointer so multiple IA options in one message reuse the same Reconfigure authentication key. A DHCPv6 REQUEST from an adjacent-network client can make the first IA set `first`, then make a later same-IAID IA fail the on-link check and free that same lease, leaving `first` dangling. A following IA in the same packet allocates a new lease and copies `first->key`, producing a 16-byte heap-use-after-free read. ASan confirms the UAF; native tracing shows the packet shape can deterministically reclaim the freed lease as the destination allocation, producing a zeroed Reconfigure key copy. The validated impact is unauthenticated adjacent-network denial of service and DHCPv6 Reconfigure/ForceRenew key confusion. Arbitrary PC control is not proven for this UAF alone. This issue has been patched in version 25.12.

## Affected

- `odhcpd < 25.12`

## Remediation

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