CVE-2026-53921
CRITICAL 9.8odhcpd 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.
Severe if exploited (CVSS 9.8), but no known exploitation and low modeled probability. Patch on a normal cadence.
Exploitation likelihood
1.1%chance of exploitation in 30 days · 66th percentile
Impact if exploited
9.8CVSS 3.1 · CRITICAL
- ConfidentialityHigh
- IntegrityHigh
- AvailabilityHigh
What an attacker needs
- ✓Access: Reachable over the network — no local access needed
- ✓Privileges: No account or privileges required
- ✓User interaction: No user interaction needed
- ✓Complexity: No special conditions — reliably repeatable
✓ lowers the bar for an attacker · ⚠ raises it
Proof of concept
No public PoC is currently catalogued.
Search for new PoCs
Search GitHub now — results may be empty or unverified.
Tracked sources are checked daily for recent CVEs, including PoCs published after the original disclosure. A later release appears after a tracked source lists it and a refresh succeeds.
Data snapshot:
Weakness (CWE)
- CWE-121: : Stack-based Buffer Overflow
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
References and research data (JSON)
Unverified PoC candidates
Catalogue matches for further research. These repositories have not been validated as working exploits.
2 candidates
- https://github.com/0xBlackash/CVE-2026-53921
CVE-2026-53921
PoC-in-GitHub · CVE-2026-53921
PoC-in-GitHub · CVE-2026-53921 · Updated 2026-08-04T23:46:23Z - https://github.com/tc4dy/CVE-2026-53921-PoC-Exploit
CVE-2026-53921 – odhcpd Stack Overflow (CVSS 9.8) Vuln detailed and comprehensive Write-Up and Verifier & Multi-exploit for OpenWrt DHCPv6 RCE. Dual-vector (IA_NA/IA_PD) overflow with MIPS/ARM shellcode, ROP chains, SOCKS5 proxy, persistence, log wiping & mass scanning. Use Ethically, Stay Legal.
PoC-in-GitHub · CVE-2026-53921
PoC-in-GitHub · CVE-2026-53921 · Updated 2026-10-09T03:58:35Z
All CVSS metrics
- CRITICAL 9.8 v3.1 · CNA Primary
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - CRITICAL 9.8 v3.1 · NVD Secondary
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
References
Advisories
- https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-108966 EUVD · EUVD-2026-108966
Technical & other
- https://github.com/openwrt/odhcpd/security/advisories/GHSA-7fwx-hhrg-3496 CVE record · GitHub_M · Updated 2026-10-23T13:20:30.249Z
NVD · CVE-2026-53921 · Updated 2026-10-23T19:37:11.060 - https://github.com/openwrt/odhcpd/commit/0320032ae313452f3c8cb8725c621dd06c36dc03 CVE record · GitHub_M · Updated 2026-10-23T13:20:30.249Z
NVD · CVE-2026-53921 · Updated 2026-10-23T19:37:11.060 - https://github.com/openwrt/odhcpd/commit/03dacc23356b5789842b9d1bba0200fd005e35f3 CVE record · GitHub_M · Updated 2026-10-23T13:20:30.249Z
NVD · CVE-2026-53921 · Updated 2026-10-23T19:37:11.060 - https://github.com/openwrt/odhcpd/commit/2a42d34c3615e2449ca273f673eee7c429d819a9 CVE record · GitHub_M · Updated 2026-10-23T13:20:30.249Z
NVD · CVE-2026-53921 · Updated 2026-10-23T19:37:11.060 - https://github.com/openwrt/odhcpd/commit/6634b7a3c79c41a27687925c98c35c8aea2f2b5a CVE record · GitHub_M · Updated 2026-10-23T13:20:30.249Z
NVD · CVE-2026-53921 · Updated 2026-10-23T19:37:11.060 - https://github.com/openwrt/odhcpd/commit/d168c27fb6a55a07ac4c888e09ff2f41e263d7b7 CVE record · GitHub_M · Updated 2026-10-23T13:20:30.249Z
NVD · CVE-2026-53921 · Updated 2026-10-23T19:37:11.060 - https://github.com/openwrt/odhcpd/commit/d329a15413387027453644cd363dca06ade28328 CVE record · GitHub_M · Updated 2026-10-23T13:20:30.249Z
NVD · CVE-2026-53921 · Updated 2026-10-23T19:37:11.060