{"id":"CVE-2026-53921","aliases":["EUVD-2026-108966","GHSA-7fwx-hhrg-3496"],"status":"published","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.","severity":{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.01123,"percentile":0.66688,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":true,"fix_available":false},"cwes":["CWE-121"],"published":"2026-10-23T13:20:30Z","modified":"2026-10-31T07:04:49Z","exploits":[{"source":"pocgithub","id":"ashrafzaryouh/CVE-2026-53921","title":"ashrafzaryouh/CVE-2026-53921","date":"2026-07-28","url":"https://github.com/ashrafzaryouh/CVE-2026-53921"},{"source":"pocgithub","id":"tc4dy/CVE-2026-53921-PoC-Exploit","title":"tc4dy/CVE-2026-53921-PoC-Exploit","date":"2026-07-28","url":"https://github.com/tc4dy/CVE-2026-53921-PoC-Exploit"}],"products":[{"vendor":"openwrt","product":"odhcpd"}],"references":[{"url":"https://github.com/openwrt/odhcpd/security/advisories/GHSA-7fwx-hhrg-3496","tags":["x_refsource_CONFIRM","exploit","advisory"]},{"url":"https://github.com/openwrt/odhcpd/commit/0320032ae313452f3c8cb8725c621dd06c36dc03","tags":["x_refsource_MISC","fix"]},{"url":"https://github.com/openwrt/odhcpd/commit/03dacc23356b5789842b9d1bba0200fd005e35f3","tags":["x_refsource_MISC","fix"]},{"url":"https://github.com/openwrt/odhcpd/commit/2a42d34c3615e2449ca273f673eee7c429d819a9","tags":["x_refsource_MISC","fix"]},{"url":"https://github.com/openwrt/odhcpd/commit/6634b7a3c79c41a27687925c98c35c8aea2f2b5a","tags":["x_refsource_MISC","fix"]},{"url":"https://github.com/openwrt/odhcpd/commit/d168c27fb6a55a07ac4c888e09ff2f41e263d7b7","tags":["x_refsource_MISC","fix"]},{"url":"https://github.com/openwrt/odhcpd/commit/d329a15413387027453644cd363dca06ade28328","tags":["x_refsource_MISC","fix"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53921.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-53921","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-53921","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.","status":"published","published":"2026-10-23T13:20:30.249Z","modified":"2026-10-29T13:28:11.455Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"cna"}],"cwes":["CWE-121"],"updated_at":"2026-11-02T14:19:59.761005Z"}],"euvd":[{"id":"EUVD-2026-108966","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.","status":"published","published":"2026-10-23T13:20:30Z","modified":"2026-10-29T13:28:11Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T16:59:16.844933Z"}],"nvd":[{"id":"CVE-2026-53921","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.","status":"published","published":"2026-10-23T14:17:53.71Z","modified":"2026-10-29T14:17:56.28Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"secondary"}],"cwes":["CWE-121"],"updated_at":"2026-11-02T14:13:03.126833Z"}],"osv":[{"id":"CVE-2026-53921","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.","status":"published","published":"2026-10-23T13:20:30.249Z","modified":"2026-10-31T07:04:49.495902353Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-121"],"updated_at":"2026-11-02T15:45:08.132336Z"}]}}