CVE-2026-112710 in Fireware OS
Summary
by MITRE • 10/27/2026
A heap-based buffer overflow vulnerability exists 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 represents a critical security flaw within the FortiGate Firewall operating system, specifically located in the authentication service module responsible for handling communications with external identity providers such as Active Directory servers. This heap-based buffer overflow arises from improper validation of input data received during the authentication handshake process. When an attacker who has the capability to control or intercept network traffic directed toward a configured Active Directory server crafts a malicious response, they can exploit this memory management error. The vulnerability allows for arbitrary write operations within the application's heap space, which is a fundamental mechanism used by dynamic memory allocation routines in C and C++ based software systems like FortiOS.
From a technical perspective, heap-based buffer overflows are particularly dangerous because they do not necessarily cause an immediate crash upon execution of the overflowed data. Instead, attackers can manipulate metadata structures within the heap allocator to achieve arbitrary code execution or trigger specific denial-of-service conditions by corrupting memory pointers and control flow integrity mechanisms. In this context, the attacker crafts a specially formatted response packet that exceeds the expected buffer size allocated for processing authentication tokens or user credentials. By carefully constructing the payload, the adversary can overwrite adjacent memory regions, potentially overwriting function return addresses or object vtables to redirect program execution to shellcode injected into the heap space.
The operational impact of this vulnerability is severe and multifaceted. Primarily, it enables a remote denial-of-service attack where an attacker can crash the authentication service process on the firewall appliance. This results in the inability for legitimate users to authenticate through Active Directory, effectively locking out authorized personnel from accessing network resources protected by the FortiGate device. Furthermore, if the exploitation conditions are met with sufficient precision and environmental factors align favorably, such as specific compiler optimizations or memory layout configurations, an attacker could achieve remote code execution with the privileges of the compromised service account. This level of access allows for complete compromise of the firewall's configuration, potential pivoting into internal networks, and exfiltration of sensitive data traversing the protected perimeter.
This vulnerability aligns closely with Common Weakness Enumeration identifier CWE-120, which describes buffer overflow without bounds checking, specifically in a heap context. It also maps to MITRE ATT&CK techniques related to initial access via compromised credentials or service account exploitation, as well as defense evasion through memory corruption to bypass security controls. The attack vector is classified as network-based and requires the attacker to have visibility into traffic between the firewall and its configured directory server, suggesting that internal network segmentation or encrypted communication channels such as LDAPS are critical mitigating factors against this specific threat scenario.
To mitigate this risk, organizations must ensure that their FortiGate appliances are updated with the latest firmware versions provided by Fortinet, which include patches for this heap overflow issue. Additionally, administrators should enforce strict access controls on Active Directory servers to prevent unauthorized entities from intercepting or spoofing authentication responses. Implementing mutual TLS authentication between the firewall and directory services can further reduce the attack surface by ensuring that only trusted parties participate in the authentication exchange. Regular vulnerability scanning and monitoring of network traffic for anomalous patterns related to LDAP or Kerberos protocols are also recommended practices to detect potential exploitation attempts before they result in system compromise.