CVE-2022-33871 in FortiWeb
Summary
by MITRE • 02/16/2023
A stack-based buffer overflow vulnerability [CWE-121] in FortiWeb version 7.0.1 and earlier, 6.4 all versions, version 6.3.19 and earlier may allow a privileged attacker to execute arbitrary code or commands via specifically crafted CLI `execute backup-local rename` and `execute backup-local show` operations.
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Analysis
by VulDB Data Team • 03/16/2023
This vulnerability represents a critical stack-based buffer overflow flaw classified under CWE-121 that affects FortiWeb web application firewalls across multiple version ranges including 7.0.1 and earlier, all 6.4 versions, and 6.3.19 and earlier. The vulnerability specifically manifests when processing command line interface operations, particularly the `execute backup-local rename` and `execute backup-local show` commands. The flaw occurs due to insufficient bounds checking in the handling of user-supplied input parameters within the stack memory allocation process. Attackers can exploit this weakness by crafting malicious input strings that exceed the allocated buffer size, leading to memory corruption that can be leveraged for arbitrary code execution.
The operational impact of this vulnerability is severe as it allows a privileged attacker to gain full control over the affected FortiWeb appliance. This represents a privilege escalation scenario where an attacker with access to the CLI interface can manipulate the system's memory layout to overwrite critical program execution elements. The vulnerability's exploitation potential aligns with ATT&CK technique T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation. Successful exploitation could result in complete system compromise, data exfiltration, and the ability to establish persistent access to the network infrastructure protected by the vulnerable FortiWeb appliance.
The technical implementation of this vulnerability stems from improper input validation within the FortiWeb CLI processing modules. When the system processes the backup-local commands, it fails to adequately validate the length of input parameters before copying them into fixed-size stack buffers. This creates a condition where attacker-controlled data can overwrite adjacent memory locations, potentially corrupting return addresses, function pointers, or other critical execution metadata. The vulnerability's classification as CWE-121 indicates that it involves a classic stack-based buffer overflow where the buffer is allocated on the stack and the overflow occurs when data exceeds the allocated space.
Organizations must implement immediate mitigations including updating to the latest FortiWeb versions that contain patches for this vulnerability, applying the vendor's security advisory, and restricting CLI access to only trusted administrators. Network segmentation and access controls should be enforced to limit exposure of the vulnerable appliance to untrusted networks. Security monitoring should focus on detecting unusual CLI command patterns and anomalous backup operations that might indicate exploitation attempts. The vulnerability's presence in multiple version lines underscores the importance of comprehensive patch management across all FortiWeb deployments. Organizations should also consider implementing additional security controls such as intrusion detection systems to monitor for exploitation patterns and maintain detailed audit logs of CLI activities for forensic analysis purposes.