{"id":"CVE-2026-53921","published":"2026-10-23T14:17:53.710","lastModified":"2026-10-23T19:37:11.060","description":"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.","cvssScore":9.8,"cvssSeverity":"CRITICAL","cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cwes":["CWE-121"],"vendors":[],"products":[],"references":[{"url":"https://github.com/openwrt/odhcpd/commit/0320032ae313452f3c8cb8725c621dd06c36dc03","tags":[]},{"url":"https://github.com/openwrt/odhcpd/commit/03dacc23356b5789842b9d1bba0200fd005e35f3","tags":[]},{"url":"https://github.com/openwrt/odhcpd/commit/2a42d34c3615e2449ca273f673eee7c429d819a9","tags":[]},{"url":"https://github.com/openwrt/odhcpd/commit/6634b7a3c79c41a27687925c98c35c8aea2f2b5a","tags":[]},{"url":"https://github.com/openwrt/odhcpd/commit/d168c27fb6a55a07ac4c888e09ff2f41e263d7b7","tags":[]},{"url":"https://github.com/openwrt/odhcpd/commit/d329a15413387027453644cd363dca06ade28328","tags":[]},{"url":"https://github.com/openwrt/odhcpd/security/advisories/GHSA-7fwx-hhrg-3496","tags":[]}],"exploitRefs":[{"url":"https://github.com/openwrt/odhcpd/commit/0320032ae313452f3c8cb8725c621dd06c36dc03","tags":[]},{"url":"https://github.com/openwrt/odhcpd/commit/03dacc23356b5789842b9d1bba0200fd005e35f3","tags":[]},{"url":"https://github.com/openwrt/odhcpd/commit/2a42d34c3615e2449ca273f673eee7c429d819a9","tags":[]},{"url":"https://github.com/openwrt/odhcpd/commit/6634b7a3c79c41a27687925c98c35c8aea2f2b5a","tags":[]},{"url":"https://github.com/openwrt/odhcpd/commit/d168c27fb6a55a07ac4c888e09ff2f41e263d7b7","tags":[]},{"url":"https://github.com/openwrt/odhcpd/commit/d329a15413387027453644cd363dca06ade28328","tags":[]},{"url":"https://github.com/openwrt/odhcpd/security/advisories/GHSA-7fwx-hhrg-3496","tags":[]}],"hasPoc":true,"ai":{"summary":"odhcpd contains a stack-based buffer overflow in its DHCPv6 IA response handler, where crafted requests with many IA options can write past a 512-byte stack buffer (pdbuf), enabling remote code execution as root on OpenWrt devices lacking modern mitigations.","exploitability":"Exploitation is straightforward for an unauthenticated attacker over the network via a single UDP packet, requiring only knowledge of the vulnerable service endpoint and no user interaction.","blast_radius":"Successful exploitation grants full system compromise (CIA impact) on affected OpenWrt devices, with potential for persistent backdoor deployment or lateral movement within local networks.","remediation":"Upgrade to odhcpd version 25.12 or later.","detection":"No reliable host or network indicator is derivable from the published description.","tags":["stack-overflow","rce","unauth-access","embedded","openwrt"],"model":"garnet-coder","analyzedAt":"2026-10-24T09:01:51.943Z"}}