CVE-2026-112709 in Fireware OS
Summary
by MITRE • 10/27/2026
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.
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Analysis
by VulDB Data Team • 10/27/2026
The identified vulnerability resides within the authentication service component of WatchGuard Firebox Operating System, specifically affecting how the system processes responses from an external Active Directory server during the login process. This flaw is classified as a heap-based buffer overflow, which occurs when data written to a dynamically allocated memory region exceeds its designated boundary. In this specific context, the vulnerability is triggered by the authentication service parsing and handling incoming network traffic destined for or originating from the configured Active Directory infrastructure. An attacker who possesses the ability to control or intercept traffic between the Firebox appliance and the Active Directory server can exploit this weakness by injecting a specially crafted response packet that contains oversized or malformed data fields intended for user authentication validation.
From a technical perspective, heap-based buffer overflows are particularly dangerous because they allow an attacker to overwrite adjacent memory structures on the heap, which is used for dynamic memory allocation during runtime. By manipulating these memory regions, an adversary can corrupt internal application state variables, function pointers, or exception handlers. This corruption provides a mechanism to alter the control flow of the program execution. Depending on the specific version of Fireware OS and the exact layout of the heap at the time of exploitation, this could lead to arbitrary code execution with the privileges of the compromised service account. Alternatively, if the memory corruption is not precisely controlled for code injection purposes, it will likely result in a segmentation fault or similar critical error that causes the authentication service process to crash immediately.
The operational impact of this vulnerability is severe due to its potential dual nature as both a denial-of-service vector and an arbitrary code execution pathway. If exploited solely for disruption, the resulting crash of the authentication service effectively halts user logins through Active Directory integration, leading to a significant availability outage for organizations relying on centralized identity management. For enterprises where network access control is tied directly to AD credentials, this could mean that legitimate users are locked out while attackers may attempt further exploitation within the internal network segment if they have already gained some level of foothold or interception capability. If exploited for code execution, an attacker gains a high-privilege shell on the firewall appliance itself. Since firewalls act as critical gateways between trusted and untrusted networks, compromising this device allows the adversary to bypass perimeter defenses, inspect encrypted traffic via man-in-the-middle techniques if certificates are compromised, or pivot deeper into the internal network infrastructure with minimal resistance.
This vulnerability aligns closely with Common Weakness Enumeration identifier CWE-120, which describes buffer overflow without bounds checking in C and C++ programs where memory is allocated on the heap rather than the stack. The exploitation scenario also maps to MITRE ATT&CK techniques related to Initial Access via Valid Accounts or Exploitation for Credential Access, specifically leveraging weaknesses in authentication mechanisms. Furthermore, if code execution is achieved, it relates to lateral movement and privilege escalation tactics within the enterprise environment.
Mitigation strategies must focus on both immediate remediation and long-term architectural hardening. The primary defense is applying the vendor-provided software update or patch that addresses this specific heap overflow issue as soon as possible after verification in a non-production environment. Until patches are applied, network segmentation should be enforced to ensure that only authorized Active Directory servers can communicate with the firewall's authentication service interface on the required ports. Additionally, implementing strict input validation and length checks at any intermediate proxy or load balancer layer between clients and the AD server may help filter out malformed packets before they reach the vulnerable application logic. Organizations should also review their logging configurations to detect unusual patterns in authentication failures or service restarts that might indicate an ongoing exploitation attempt. Regular vulnerability scanning of network infrastructure components is essential to identify such misconfigurations or outdated software versions across the enterprise estate.