{"id":"CVE-2026-53921","revision":null,"records":[{"revision":"16e8b6eec1924f208d52e815b648b1bc","observedAt":"2026-10-23T16:01:20.601+00:00","statement":{"source":"cve-program","id":"CVE-2026-53921","aliases":[],"title":"odhcpd: Stack buffer overflow in DHCPv6 IA reply serialization (2 independent sites)","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.","state":0,"publishedAt":"2026-10-23T13:20:30.249+00:00","modifiedAt":"2026-10-23T13:20:30.249+00:00","affected":[{"ecosystem":"Vendor product","name":"odhcpd","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"openwrt\",\n                    \"product\": \"odhcpd\",\n                    \"versions\": [\n                        {\n                            \"version\": \"< 25.12\",\n                            \"status\": \"affected\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","score":9.8,"severity":"CRITICAL"}],"references":["https://github.com/openwrt/odhcpd/security/advisories/GHSA-7fwx-hhrg-3496","https://github.com/openwrt/odhcpd/commit/0320032ae313452f3c8cb8725c621dd06c36dc03","https://github.com/openwrt/odhcpd/commit/03dacc23356b5789842b9d1bba0200fd005e35f3","https://github.com/openwrt/odhcpd/commit/2a42d34c3615e2449ca273f673eee7c429d819a9","https://github.com/openwrt/odhcpd/commit/6634b7a3c79c41a27687925c98c35c8aea2f2b5a","https://github.com/openwrt/odhcpd/commit/d168c27fb6a55a07ac4c888e09ff2f41e263d7b7","https://github.com/openwrt/odhcpd/commit/d329a15413387027453644cd363dca06ade28328"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-53921","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-53921","identifiers":["CVE-2026-53921"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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