CVE-2026-53921 Details
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.
A stack buffer overflow vulnerability has been identified in the odhcpd DHCPv6 server used by OpenWrt, prior to version 25.12. The issue arises in the DHCPv6 IA response handler, which writes past the end of a fixed 512-byte stack buffer (pdbuf) when a single DHCPv6 REQUEST includes enough IA options to nearly exhaust the available reply space. This vulnerability is present in all versions prior to 25.12 that contain the 'dhcpv6_ia_handle_IAs()' and 'build_ia()' functions. The overflow can be triggered by a single unauthenticated UDP packet, and since odhcpd runs as root on OpenWrt, this could potentially lead to arbitrary code execution, especially on embedded devices that lack stack canaries and address space layout randomization (ASLR).
Users can upgrade to odhcpd version 25.12 or later, where this vulnerability has been patched.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Oct 23, 2026CISA-ADP
Assessed Oct 29, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/openwrt/odhcpd/security/advisories/GHSA-7fwx-hhrg-3496 | CISA-ADP | AdvisoryExploitRemedyVendor |
| https://github.com/openwrt/odhcpd/commit/0320032ae313452f3c8cb8725c621dd06c36dc03 | [email protected] | Source CodeVendor |
| https://github.com/openwrt/odhcpd/commit/03dacc23356b5789842b9d1bba0200fd005e35f3 | [email protected] | Source CodeVendor |
| https://github.com/openwrt/odhcpd/commit/2a42d34c3615e2449ca273f673eee7c429d819a9 | [email protected] | Source CodeVendor |
| https://github.com/openwrt/odhcpd/commit/6634b7a3c79c41a27687925c98c35c8aea2f2b5a | [email protected] | Source CodeVendor |
| https://github.com/openwrt/odhcpd/commit/d168c27fb6a55a07ac4c888e09ff2f41e263d7b7 | [email protected] | Source CodeVendor |
| https://github.com/openwrt/odhcpd/commit/d329a15413387027453644cd363dca06ade28328 | [email protected] | Source CodeVendor |
| https://github.com/openwrt/odhcpd/security/advisories/GHSA-7fwx-hhrg-3496 | [email protected] | AdvisoryExploitRemedyVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-121 | Stack-based Buffer Overflow | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| odhcpd | <= master (e432dd6) |
CPE
Remediation
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Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Oct 29, 2026 | CVE Modified | CISA-ADP |
| Oct 23, 2026 | New CVE Received | [email protected] |