CVE-2026-53922 odhcpd: pre-auth remote DoS via size_t underflow in dhcpv6_ia_handle_IAs (stack BOF, canary-terminated)
An unauthenticated attacker can cause a denial of service in OpenWrt's odhcpd by triggering a size_t underflow that leads to a stack buffer overflow and process crash.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-53922?
CVE-2026-53922 is a medium-severity vulnerability in openwrt odhcpd, published on 12 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt. In commit cfddd56 and earlier, an unauthenticated host on the same link can first obtain two bindings through normal DHCPv6 SOLICIT and REQUEST exchanges and then send a crafted RENEW containing multiple IA_NA options. An earlier matched IA consumes most of the response buffer, an unmatched IA causes the build_ia() status branch to write and return a NOBINDING response larger than the remaining space, and a subsequent matched IA is processed after dhcpv6_ia_handle_IAs() subtracts that over-return from an unsigned size_t. The resulting underflow disables subsequent length checks and permits attacker-controlled IA_ADDR serialization beyond the 512-byte stack buffer pdbuf in handle_client_request(). The stack canary terminates odhcpd, and sustained packets can repeatedly disrupt DHCPv6 service while procd respawns the process. The observed configuration does not establish code execution.
Which versions are affected by CVE-2026-53922?
How do I fix CVE-2026-53922?
No fix has been published for CVE-2026-53922 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-53922 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53922 exists.
Sources
Also known as GHSA-7hcw-g2jh-pqv5.