CVE-2026-53921
CVE-2026-53921 · odhcpd: Stack buffer overflow in DHCPv6 IA reply serialization (2 independent sites)
This page contains facts from public vulnerability sources. Check the original advisory before updating.
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.
CVSS 9.8 · Critical · Public exploit
- Published
- Updated
Affected products and versions
odhcpd
- Versions
- < 25.12: Affected
No fix published
Original sources
- 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
- https://nvd.nist.gov/vuln/detail/CVE-2026-53921