Firebox and Fireware OS
CVE-2026-86133: Fireware OS Pre-Authentication Integer Underflow in iked Allows Remote Denial of Service
An integer underflow vulnerability in the WatchGuard Fireware OS IKE daemon (iked) allows a remote attacker who has completed the initial IKEv2 handshake to crash the iked process by sending a specially crafted encrypted IKEv2 message, resulting in a denial of service.
Published
Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.
Affected and fixed versions
| Product / branch | Fixed in |
|---|---|
| Fireware OS (Default) 2026.3 | 2026.3.2 or later |
| Fireware OS (Default) 2025.0 | 2026.2.3 or later |
| Fireware OS (Default) 12.0 | 12.12.3 or later |
| Fireware OS (T15/T35) 12.0 | 12.5.21 or later |
Always confirm against the vendor advisory, which lists every fixed hotfix.
What it is
An integer underflow vulnerability in the WatchGuard Fireware OS IKE daemon (iked) allows a remote attacker who has completed the initial IKEv2 handshake to crash the iked process by sending a specially crafted encrypted IKEv2 message, resulting in a denial of service.
Am I affected?
This vulnerability affects Firebox systems configured with a branch office VPN with IKEv2 to a dynamic peer or a mobile VPN with IKEv2
Exploitation
WatchGuard is not aware of any exploitation of this vulnerability in the wild.
Sources
KEV status, EPSS score and vendor data refreshed automatically, last on 13 Oct 2026.