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CVE-2026-55606— odhcpd: Stack buffer overread via DUID length endianness mismatch in memcmp()

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 和路由器通告（Router Advertisement）服务器软件。在 25.12 及更早版本中，odhcpd 在 dhcpv6.c 第 720 行实现的 DHCPv6 自环检测功能，错误地将采用网络字节序的 DUID 长度值直接用作 memcmp() 函数的 size 参数。在小端序（little-endian）主机上，这会导致 memcmp() 读取远超栈缓冲区范围的数据——单个未经认证的 DHCPv6 数据包即可引发从 128 字节缓冲区

CVSS 6.5 · Medium

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-2026-55606

Vulnerability Information
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Vulnerability Title
odhcpd: Stack buffer overread via DUID length endianness mismatch in memcmp()
Source: CVE Program / CVE List V5
Vulnerability Description
odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt. In versions 25.12 and prior, odhcpd's DHCPv6 self-loop detection at dhcpv6.c:720 uses a network-byte-order DUID length value directly as the memcmp() size parameter. On little-endian hosts, this causes memcmp() to read far beyond the stack buffer — a single unauthenticated DHCPv6 packet triggers a 2560-byte overread from a 128-byte buffer. At time of publication, there are no publicly available patches.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
缓冲区上溢读取
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
openwrt odhcpd <= 25.12 -

II. Public POCs for CVE-2026-55606

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III. Intelligence Information for CVE-2026-55606

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Patches & Fixes for CVE-2026-55606 (3)

Vendor Advisories for CVE-2026-55606 (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-2026-53918 8.8 HIGH odhcpd DHCPv6 IA dangling first pointer use-after-free
CVE-2026-53920 8.7 HIGH odhcpd DHCPv6 Short IA_NA/IA_PD Body Stack Disclosure

IV. Related Vulnerabilities

Same product: odhcpd
Same vendor: openwrt
Same weakness: CWE-126

V. Comments for CVE-2026-55606

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