CVE-2026-53918
HIGHDescription
odhcpd 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.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v4 Vector
Exploitability
Impact
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
Exploit Intelligence
Moderate risk: more likely to be exploited than 43% of all known CVEs.
References
Related Vulnerabilities
Other CWE-416 (Use After Free) vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2026-109619 | High | 8.1 | 100% | KEV | Fix |
| CVE-2026-109618 | Critical | 9.8 | 100% | KEV | Fix |
| CVE-2019-0708 | Critical | 9.8 | 100% | KEV + Ransom | - |
| CVE-2021-31166 | Critical | 9.8 | 100% | KEV | Fix |
| CVE-2015-5119 | Critical | 9.8 | 99% | KEV | - |
| CVE-2010-3962 | High | 8.1 | 97% | KEV | - |
Common questions
How do I fix CVE-2026-53918?
No published fix for CVE-2026-53918 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-53918 being actively exploited?
Not that we know of. CVE-2026-53918 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.50% is the estimated probability that it will be exploited in the next 30 days. That is higher than 43% of all scored CVEs.
How severe is CVE-2026-53918?
CVE-2026-53918 has a CVSS v4 base score of 8.8, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-10-23.