What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-23 · updated 2026-10-29
• Weakness: CWE-126

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.

Affected products

• openwrt odhcpd: through 25.12

References

• https://github.com/openwrt/odhcpd/commit/6907f28f9ddeef9f69f5ee10bbc9ba8adc0ef57f
• https://github.com/openwrt/odhcpd/commit/ed38cffa927d5fd450d20bfd3f7fb8d8e8fff301
• https://github.com/openwrt/odhcpd/pull/401
• https://github.com/openwrt/odhcpd/security/advisories/GHSA-x8x4-7gvf-gp45
• https://github.com/openwrt/odhcpd/security/advisories/GHSA-x8x4-7gvf-gp45

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