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CVE-2026-53921

odhcpd: Stack buffer overflow in DHCPv6 IA reply serialization (2 independent sites) PUBLISHED

Description (CNA)

odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt. Prior to version 25.12, odhcpd's DHCPv6 IA response handler writes past the end of a fixed 512-byte stack buffer (pdbuf) when a single DHCPv6 REQUEST carries enough IA options to nearly exhaust the reply space. Two independent overflow sites exist in the same call chain, both reachable from the network via a single unauthenticated UDP packet. odhcpd runs as root on OpenWrt; embedded targets often lack stack canaries and ASLR, making code execution realistic. This issue has been patched in version 25.12.

Affected (CNA)

Vendor / productVersions
openwrt / odhcpdaffected < 25.12

CWE

CWE-121

References