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CVE-2026-53918— odhcpd DHCPv6 IA dangling first pointer use-after-free

Quick assessment

Affected
openwrt odhcpd
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

odhcpd 是 OpenWrt 所使用的 DHCPv6、DHCPv4 及路由器通告（Router Advertisement）服务器。在版本 25.12 之前，odhcpd 的 DHCPv6 IA（地址授权）处理程序会为每条消息维护一个名为 的租约指针，导致同一消息中的多个 IA 选项复用相同的重配置（Reconfigure）认证密钥。来自相邻网络客户端的 DHCPv6 REQUEST 请求可先使第一个 IA 将 指针指向某个租约，随后使后续具有相同 IAID 的 IA 因未通过链路检查而释放该租约，导致 指针悬

CVSS 8.8 · High

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
openwrt odhcpd < 25.12 affected
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I. Basic Information for CVE-2026-53918

Vulnerability Information
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Vulnerability Title
odhcpd DHCPv6 IA dangling first pointer use-after-free
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
释放后使用
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
openwrt odhcpd < 25.12 -

II. Public POCs for CVE-2026-53918

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III. Intelligence Information for CVE-2026-53918

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Patches & Fixes for CVE-2026-53918 (2)

Vendor Advisories for CVE-2026-53918 (1)

Same Patch Batch · openwrt · 2026-10-23 · 4 CVEs total

CVE-2026-53921 9.8 CRITICAL odhcpd: Stack buffer overflow in DHCPv6 IA reply serialization (2 independent sites)
CVE-2026-53920 8.7 HIGH odhcpd DHCPv6 Short IA_NA/IA_PD Body Stack Disclosure
CVE-2026-55606 6.5 MEDIUM odhcpd: Stack buffer overread via DUID length endianness mismatch in memcmp()

IV. Related Vulnerabilities

Same product: odhcpd
Same vendor: openwrt
Same weakness: CWE-416

V. Comments for CVE-2026-53918

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