{"schema":"threatline.record/2","record":{"id":"CVE-2026-53921","aliases":["GHSA-7fwx-hhrg-3496"],"summary":"odhcpd: Stack buffer overflow in DHCPv6 IA reply serialization (2 independent sites)","details":"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.","categories":["Network & edge"],"product":"odhcpd","vendor":"openwrt","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-53921","source_modified_at":"2026-10-23T13:20:30.249Z","fetched_at":"2026-10-23T18:42:43.628194Z","product":"odhcpd","vendor":"openwrt","versions":[{"status":"affected","version":"< 25.12"}],"defaultStatus":null}],"fixed_versions":[],"cvss":9.8,"severity":"Critical","kev":{"listed":false},"epss":{"probability":0.0088,"percentile":0.58778,"score_date":"2026-10-24"},"published_at":"2026-10-23T13:20:30.249Z","modified_at":"2026-10-23T13:20:30.249Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-53921","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23T13:20:30.249Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-53921","fetched_at":"2026-10-24T18:03:20.872036Z","source_modified_at":"2026-10-24"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://github.com/openwrt/odhcpd/security/advisories/GHSA-7fwx-hhrg-3496","tags":["x_refsource_CONFIRM"]},{"source":"CVE List","url":"https://github.com/openwrt/odhcpd/commit/0320032ae313452f3c8cb8725c621dd06c36dc03","tags":["x_refsource_MISC"]},{"source":"CVE List","url":"https://github.com/openwrt/odhcpd/commit/03dacc23356b5789842b9d1bba0200fd005e35f3","tags":["x_refsource_MISC"]},{"source":"CVE List","url":"https://github.com/openwrt/odhcpd/commit/2a42d34c3615e2449ca273f673eee7c429d819a9","tags":["x_refsource_MISC"]},{"source":"CVE List","url":"https://github.com/openwrt/odhcpd/commit/6634b7a3c79c41a27687925c98c35c8aea2f2b5a","tags":["x_refsource_MISC"]},{"source":"CVE List","url":"https://github.com/openwrt/odhcpd/commit/d168c27fb6a55a07ac4c888e09ff2f41e263d7b7","tags":["x_refsource_MISC"]},{"source":"CVE List","url":"https://github.com/openwrt/odhcpd/commit/d329a15413387027453644cd363dca06ade28328","tags":["x_refsource_MISC"]}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","cvss_source":"CVE List","classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"vendor and product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-23T13:20:30.249Z","content_hash":"dbcb925e6680154c644b5381423ffd14cc0a82534b086e18d5a8fdd1dbf8647c"}}