WatchGuard Fireware OS: Heap buffer overflow in AD authentication service
Summary
A heap-based buffer overflow in the Fireware OS authentication service affects Firebox firewalls configured with an Active Directory authentication server. An attacker who controls or intercepts traffic to the configured AD server can send a specially crafted response to cause a denial of service and potentially execute arbitrary code. The vendor describes the issue as pre-authentication, and the CVSS v4.0 score is 9.2 (critical).
Affected
- Fireware OS default branch: 2025.1 to before 2026.4, and 12.0 to before 12.12.4
- Fireware OS T15/T35 devices: 12.0 to before 12.5.22
- Only Firebox deployments configured with an Active Directory authentication server are affected.
Fixed in
- Fireware OS 2026.4 (default branch)
- Fireware OS 12.12.4 (default branch, 12.x)
- Fireware OS 12.5.22 (T15/T35)
Workaround
- Unknown. The vendor gives no workaround; apply the fixed release.
- Interim (recommendation, not from the vendor): restrict network paths to the AD server and monitor AD authentication traffic for anomalies.
Exploitation
- WatchGuard is not aware of any exploitation in the wild.
- No public proof-of-concept confirmed; not listed in CISA KEV.
- Attacker must be able to control or intercept traffic to the AD server (on-path position).
Our recommendation
- Identify all Firebox devices and their firmware branch (default or T15/T35).
- Check whether Active Directory authentication is configured.
- Upgrade to 2026.4, 12.12.4 or 12.5.22, depending on the branch.
- If patching is delayed, restrict which networks can reach the AD server path and monitor AD authentication traffic.
- Recheck the NVD record and the WatchGuard PSIRT page for changes.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- WatchGuard PSIRT advisory CVE-2026-112709 psirt.watchguard.com
- VulDB entry 427418 vuldb.com
- Rapid7 vulnerability database entry www.rapid7.com
- Strix CVE record CVE-2026-112709 www.strix.ai
- Securityonline: WatchGuard Fireware OS vulnerabilities securityonline.info
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 31 Oct 2026, 04:01.
Original description (NVD)
A heap-based buffer overflow vulnerability in the Fireware OS authentication service allows an attacker who controls or intercepts traffic to the configured Active Directory server to create a denial of service condition and potentially execute arbitrary code by returning a specially crafted response.
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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