CVE-2021-42755 in FortiSwitch
Summary
by MITRE • 07/18/2022
An integer overflow / wraparound vulnerability [CWE-190] in FortiSwitch 7.0.2 and below, 6.4.9 and below, 6.2.x, 6.0.x; FortiRecorder 6.4.2 and below, 6.0.10 and below; FortiOS 7.0.2 and below, 6.4.8 and below, 6.2.10 and below, 6.0.x; FortiProxy 7.0.0, 2.0.6 and below, 1.2.x, 1.1.x, 1.0.x; FortiVoiceEnterprise 6.4.3 and below, 6.0.10 and below dhcpd daemon may allow an unauthenticated and network adjacent attacker to crash the dhcpd deamon, resulting in potential denial of service.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 10/27/2024
The vulnerability identified as CVE-2021-42755 represents a critical integer overflow condition that affects multiple Fortinet security products including FortiSwitch, FortiRecorder, FortiOS, FortiProxy, and FortiVoiceEnterprise. This flaw manifests as an integer wraparound issue classified under CWE-190, which occurs when an operation on an integer value exceeds the maximum representable value and wraps around to the minimum value, creating unpredictable behavior. The vulnerability specifically impacts dhcpd daemon components within these products, making it particularly concerning for network infrastructure devices that rely heavily on DHCP services for device provisioning and network management. The affected versions span across multiple major releases, indicating a widespread issue that has persisted across different product lines and development cycles, suggesting either a fundamental design flaw or inadequate input validation mechanisms in the dhcpd implementation.
The operational impact of this vulnerability is significant as it allows unauthenticated attackers who are network adjacent to trigger a denial of service condition by crashing the dhcpd daemon. This attack vector requires minimal privileges and can be executed from within the network segment where the vulnerable devices operate, making it particularly dangerous in environments where network segmentation is not properly enforced. When the dhcpd daemon crashes, it disrupts the dynamic host configuration protocol functionality, preventing devices from obtaining IP addresses and network configuration parameters necessary for normal network operations. The potential for cascading effects exists as network services that depend on DHCP for device discovery and configuration may become unavailable, potentially affecting critical business operations and network connectivity for multiple devices simultaneously.
From a cybersecurity perspective, this vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks, and represents a classic example of how integer overflow vulnerabilities can be exploited for service disruption. The vulnerability's presence in dhcpd daemons specifically targets the fundamental network infrastructure services that maintain connectivity and device management within enterprise environments. The fact that this issue affects multiple product lines suggests a common codebase or shared implementation pattern that was not properly validated for integer overflow conditions. Organizations should consider implementing network segmentation and access controls to limit the attack surface, as well as monitoring for unusual network behavior that might indicate exploitation attempts. The vulnerability demonstrates the importance of robust input validation and proper integer handling in network services, particularly those that process untrusted network data from external sources. Security teams should prioritize patching affected systems and implementing additional monitoring to detect potential exploitation attempts that could lead to service disruption and network availability issues.