CVE-2022-43953 in FortiOS
Summary
by MITRE • 06/13/2023
A use of externally-controlled format string in Fortinet FortiOS version 7.2.0 through 7.2.4, FortiOS all versions 7.0, FortiOS all versions 6.4, FortiOS all versions 6.2, FortiProxy version 7.2.0 through 7.2.1, FortiProxy version 7.0.0 through 7.0.7 allows attacker to execute unauthorized code or commands via specially crafted commands.
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Analysis
by VulDB Data Team • 07/08/2023
This vulnerability represents a critical format string injection flaw in Fortinet FortiOS and FortiProxy products that stems from improper input validation and sanitization of user-supplied data. The vulnerability exists in versions ranging from FortiOS 7.2.0 through 7.2.4, all 7.0 and 6.4 and 6.2 versions, as well as FortiProxy 7.2.0 through 7.2.1 and 7.0.0 through 7.0.7, creating a widespread impact across multiple product lines. The flaw allows attackers to manipulate format specifiers in input handling routines, potentially leading to arbitrary code execution or command injection.
The technical implementation of this vulnerability involves the improper use of externally-controlled format strings in the software's command processing mechanisms. When the system processes user input containing format specifiers such as %s, %d, or %x without proper validation or sanitization, attackers can craft malicious input that exploits the format string vulnerability. This allows them to read or write arbitrary memory locations, potentially leading to stack corruption, information disclosure, or complete system compromise. The vulnerability specifically targets the application's printf-like functions where user-controllable data is directly used as format strings without proper escaping or validation.
The operational impact of this vulnerability is severe and multifaceted, representing a high-risk threat to network security infrastructure. Attackers can leverage this flaw to execute unauthorized commands on affected systems, potentially gaining full administrative control over the Fortinet appliances. This could enable lateral movement within networks, data exfiltration, or disruption of critical services. The vulnerability's widespread presence across multiple FortiOS and FortiProxy versions means that organizations with legacy deployments are particularly at risk. According to the CWE classification, this maps to CWE-134, which specifically addresses the use of externally-controlled format strings, a well-known weakness that has been exploited in numerous security incidents.
The attack surface for this vulnerability extends beyond simple command execution to include potential information disclosure and system stability issues. An attacker could exploit the format string vulnerability to read sensitive memory locations, potentially extracting credentials, configuration data, or other confidential information. The attack vector typically involves sending specially crafted commands through the network interface or management protocols that trigger the vulnerable code path. This vulnerability aligns with several ATT&CK techniques including T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation, making it particularly dangerous in environments where these devices serve as network gateways or security appliances.
Organizations should implement immediate mitigations including applying the latest security patches from Fortinet, which address the format string vulnerability through proper input validation and sanitization. Network segmentation and access controls should be strengthened to limit exposure of these devices to untrusted networks. Monitoring for unusual command execution patterns or authentication attempts should be enabled to detect potential exploitation attempts. Additionally, implementing network-based intrusion detection systems with signatures for known exploitation patterns can provide early warning of attacks targeting this vulnerability. Regular security assessments and vulnerability scanning should be conducted to identify and remediate similar issues in other network infrastructure components. The vulnerability demonstrates the critical importance of input validation in security-critical applications and serves as a reminder of the potential consequences of insufficient sanitization of user-supplied data in system components that handle administrative commands.