CVE-2026-53921
odhcpd: Stack buffer overflow in DHCPv6 IA reply serialization (2 independent sites)
- State
- Published
- Severity
- 9.8 Critical
- Published
- Oct 23, 2026
- Updated
- Oct 29, 2026
- Reserved
- Jun 11, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 9.8 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H | GitHub_M |
Weaknesses
- CWE-121 Stack-based Buffer Overflow
Affected Products
| Product | Versions |
|---|---|
odhcpdopenwrt |
|
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
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