CVE-2026-53918
HIGH 8.8odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt. Prior to version 25.12, odhcpd's DHCPv6 IA handler keeps a per-message `first` lease pointer so multiple IA options in one message reuse the same Reconfigure authentication key. A DHCPv6 REQUEST from an adjacent-network client can make the first IA set `first`, then make a later same-IAID IA fail the on-link check and free that same lease, leaving `first` dangling. A following IA in the same packet allocates a new lease and copies `first->key`, producing a 16-byte heap-use-after-free read. ASan confirms the UAF; native tracing shows the packet shape can deterministically reclaim the freed lease as the destination allocation, producing a zeroed Reconfigure key copy. The validated impact is unauthenticated adjacent-network denial of service and DHCPv6 Reconfigure/ForceRenew key confusion. Arbitrary PC control is not proven for this UAF alone. This issue has been patched in version 25.12.
Severe if exploited (CVSS 8.8), but no known exploitation and low modeled probability. Patch on a normal cadence.
Exploitation likelihood
0.5%chance of exploitation in 30 days · 43rd percentile
Impact if exploited
8.8CVSS 4.0 · HIGH
- ConfidentialityNone
- IntegrityLow
- 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
- ✓Requirements: No special attack requirements
✓ lowers the bar for an attacker · ⚠ raises it
Proof of concept
No public PoC is currently catalogued.
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Data snapshot:
Weakness (CWE)
- CWE-416: : Use After Free
- CWE-672: : Operation on a Resource after Expiration or Release
- CWE-825: : Expired Pointer Dereference
CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N
References and research data (JSON)
All CVSS metrics
- HIGH 8.8 v4.0 · CNA Primary
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N - HIGH 8.8 v4.0 · NVD Secondary
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
References
Advisories
- https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-108969 EUVD · EUVD-2026-108969
Technical & other
- https://github.com/openwrt/odhcpd/security/advisories/GHSA-44ff-jcwh-wgc2 CVE record · GitHub_M · Updated 2026-10-23T13:21:00.665Z
NVD · CVE-2026-53918 · Updated 2026-10-23T19:37:11.060 - https://github.com/openwrt/odhcpd/commit/26b122007030ebf192376aff8f98d428b25e2a93 CVE record · GitHub_M · Updated 2026-10-23T13:21:00.665Z
NVD · CVE-2026-53918 · Updated 2026-10-23T19:37:11.060 - https://github.com/openwrt/odhcpd/commit/5b283832c0a77aed20f1cc384ffc40bc768b06e9 CVE record · GitHub_M · Updated 2026-10-23T13:21:00.665Z
NVD · CVE-2026-53918 · Updated 2026-10-23T19:37:11.060