WatchGuard Fireware OS: Stack buffer overflow in WireGuard configuration
Summary
A stack-based buffer overflow in the WireGuard configuration processing of WatchGuard Fireware OS affects Fireboxes configured as a FireCloud Gateway. An attacker with man-in-the-middle access to TLS-decrypted traffic between the Firebox and WatchGuard Cloud can tamper with a FireCloud Gateway configuration payload. This can cause a Denial of Service and potentially arbitrary code execution.
Affected
- Fireware OS 2026.2 up to but not including 2026.4
- Fireware OS 12.12 up to but not including 12.12.4
- Only Fireboxes configured to act as a FireCloud Gateway are affected by default configurations; default configuration is unaffected
- Versions outside these ranges are not listed as affected in the vendor advisory
Fixed in
- Fireware OS 2026.4
- Fireware OS 12.12.4
Workaround
Unknown.
Exploitation
- WatchGuard is not aware of any exploitation in the wild.
- Not listed in CISA KEV at the time of research.
- A public PoC is unverified; no working exploit code was found.
Our recommendation
- Inventory Fireboxes and check firmware against the affected ranges.
- Check whether any Firebox is configured as a FireCloud Gateway.
- Upgrade affected devices to Fireware OS 2026.4 or 12.12.4, together with the other October 2026 WatchGuard advisories, prioritising internet-facing units.
- Restrict management and VPN exposure until patched, and monitor for unusual configuration changes or device crashes.
- Confirm the final NVD record once analysis is complete.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- WatchGuard PSIRT advisory CVE-2026-103594 psirt.watchguard.com
- Strix AI CVE-2026-103594 www.strix.ai
- Firsthackersnews: WatchGuard firewalls vulnerable to critical attacks firsthackersnews.com
- ThreatInt CVE-2026-103594 cve.threatint.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 30 Oct 2026, 23:30.
Original description (NVD)
A stack-based buffer overflow vulnerability in Fireware OS's WireGuard configuration processing allows a remote attacker that has man-in-the-middle TLS-decrypted access between the Firebox and WatchGuard Cloud to create a Denial of Service condition and potentially execute arbitrary code by tampering with a FireCloud Gateway configuration payload.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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