CVE-2016-6909 in FortiOS
Summary
by MITRE
Buffer overflow in the Cookie parser in Fortinet FortiOS 4.x before 4.1.11, 4.2.x before 4.2.13, and 4.3.x before 4.3.9 and FortiSwitch before 3.4.3 allows remote attackers to execute arbitrary code via a crafted HTTP request, aka EGREGIOUSBLUNDER.
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Analysis
by VulDB Data Team • 09/24/2024
The vulnerability identified as CVE-2016-6909 represents a critical buffer overflow flaw within the cookie parsing functionality of Fortinet FortiOS versions across multiple release streams. This issue affects FortiOS 4.x versions prior to 4.1.11, 4.2.x versions before 4.2.13, 4.3.x versions before 4.3.9, and FortiSwitch before 3.4.3. The vulnerability is classified as a remote code execution flaw that can be exploited through specially crafted HTTP requests, making it particularly dangerous for network security infrastructure deployments. The vulnerability has been assigned the alias EgregiousBlunder by Fortinet, indicating its severity and potential impact on enterprise security systems.
The technical root cause of this vulnerability stems from improper input validation within the HTTP cookie parsing module of FortiOS. When the system processes HTTP requests containing malformed cookie data, the buffer overflow occurs due to insufficient bounds checking and memory management. The flaw typically manifests when an attacker sends an HTTP request with a cookie value that exceeds the allocated buffer space, causing memory corruption that can be leveraged to overwrite critical memory locations. This memory corruption can lead to arbitrary code execution with the privileges of the affected service process, potentially allowing full system compromise. The vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and represents a classic example of improper input validation in network security appliances.
The operational impact of CVE-2016-6909 extends beyond simple remote code execution, as it fundamentally compromises the security posture of affected Fortinet devices. Network administrators face the risk of complete system compromise, data exfiltration, and potential lateral movement within the network infrastructure. Attackers can exploit this vulnerability to gain unauthorized access to sensitive network information, modify security policies, or establish persistent backdoors. The impact is particularly severe for organizations relying on FortiOS for firewall and security gateway functions, as these devices often serve as critical network perimeters. The vulnerability's classification under the MITRE ATT&CK framework would fall under the T1059.007 technique for command and scripting interpreter, specifically HTTP-based command execution, and potentially T1071.001 for application layer protocol usage.
Mitigation strategies for CVE-2016-6909 require immediate implementation of firmware updates to the affected FortiOS versions, with administrators prioritizing the upgrade to patched releases. The Fortinet security advisory recommends upgrading to FortiOS 4.1.11, 4.2.13, 4.3.9, or later versions for FortiOS devices, and 3.4.3 or later for FortiSwitch appliances. Network segmentation and access control measures should be implemented to limit exposure to potentially malicious traffic, while intrusion detection systems should be configured to monitor for suspicious HTTP request patterns. Organizations should also consider implementing web application firewalls and additional network monitoring to detect exploitation attempts. The vulnerability's remediation aligns with industry best practices for vulnerability management and follows the principle of least privilege, ensuring that only necessary network services are exposed to external traffic while maintaining comprehensive logging and monitoring capabilities to detect any potential exploitation attempts.