odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt.
CVE-2026-53921 · EUVD-2026-108966 · published 23 Oct 2026
How serious is it
- Severity: critical, CVSS score 9.8 out of 10.
- No exploit prediction (EPSS) score yet.
- Not on the CISA list of exploited vulnerabilities.
- No public exploit in Exploit-DB.
Is your app affected by CVE-2026-53921?
Paste this prompt into Claude Code, Cursor or any AI coding tool: it runs a free Shippable scan of your project and fixes what it finds. Built with Lovable, Bolt or v0? Scan your live app. Or upload your package file.
Who is affected
- OpenWRT odhcpd: < 25.12
How to check
- Find out whether you run the affected product and which version, then compare it with the versions above.
How to fix
Copies a prompt for Claude Code, Cursor or Codex that asks it to check whether you run this product.
- Apply the vendor's update or mitigation from the references below. If there is none yet, limit exposure of the affected service until there is.
- If a vulnerable version was live, check your logs and rotate the secrets that server could read.
The advisory
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.
Check your whole app
Dependencies are only half of it. Free and read-only: before you push, run npx shippable-dev scan localhost:3000 in your project folder, no account needed. For your live app, you prove it's yours with a one-line tag first.
References
- github.com/openwrt/odhcpd/security/advisories/GHSA-7fwx-hhrg-3496
- github.com/openwrt/odhcpd/commit/0320032ae313452f3c8cb8725c621dd06c36dc03
- github.com/openwrt/odhcpd/commit/03dacc23356b5789842b9d1bba0200fd005e35f3
- github.com/openwrt/odhcpd/commit/2a42d34c3615e2449ca273f673eee7c429d819a9
- github.com/openwrt/odhcpd/commit/6634b7a3c79c41a27687925c98c35c8aea2f2b5a
- github.com/openwrt/odhcpd/commit/d168c27fb6a55a07ac4c888e09ff2f41e263d7b7
- github.com/openwrt/odhcpd/commit/d329a15413387027453644cd363dca06ade28328
Merged from ENISA EUVD. Last updated 23 Oct 2026. All vulnerabilities · RSS · JSON