CVE-2023-33306 in FortiOS
Summary
by MITRE • 06/16/2023
A null pointer dereference in Fortinet FortiOS before 7.2.5, before 7.0.11 and before 6.4.13, FortiProxy before 7.2.4 and before 7.0.10 allows attacker to denial of sslvpn service via specifically crafted request in bookmark parameter.
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Analysis
by VulDB Data Team • 07/14/2023
This vulnerability represents a critical null pointer dereference flaw affecting Fortinet FortiOS and FortiProxy products across multiple version ranges. The issue manifests when processing specifically crafted requests containing malicious bookmark parameters within SSL VPN services. The vulnerability stems from inadequate input validation and error handling mechanisms within the SSL VPN bookmark processing functionality, creating a condition where the application attempts to dereference a null pointer when handling malformed bookmark data. This flaw exists in the core SSL VPN service implementation and affects versions prior to 7.2.5, 7.0.11, and 6.4.13 for FortiOS, and before 7.2.4 and 7.0.10 for FortiProxy. The vulnerability is classified under CWE-476 which specifically addresses null pointer dereference conditions, representing a fundamental programming error that can lead to service disruption and potential system instability. From an operational perspective, this vulnerability enables remote attackers to execute denial of service attacks against SSL VPN services without requiring authentication, making it particularly dangerous in enterprise environments where SSL VPN access is critical for remote connectivity.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious HTTP request containing a malformed bookmark parameter and submits it to the SSL VPN service endpoint. The application fails to properly validate the bookmark parameter input, allowing the null pointer dereference to occur during subsequent processing. This condition causes the SSL VPN service to crash or become unresponsive, effectively denying legitimate users access to the VPN service. The impact extends beyond simple service disruption as the vulnerability can be exploited repeatedly, potentially leading to sustained denial of service conditions that can affect business continuity. The attack vector is remote and requires no authentication, making it particularly attractive to threat actors seeking to disrupt business operations. The vulnerability operates at the application layer and can be exploited through standard network traffic without requiring specialized tools or techniques, which increases the attack surface and potential impact.
Organizations utilizing affected Fortinet products face significant operational risks from this vulnerability, particularly in environments where SSL VPN services are heavily relied upon for remote access. The vulnerability can be exploited to disrupt critical business processes, especially in scenarios where remote workers depend on SSL VPN connectivity for accessing corporate resources. The attack can result in unauthorized service disruption, potentially affecting productivity and customer service availability. From a security posture perspective, this vulnerability creates an opportunity for attackers to perform reconnaissance activities or establish persistent access points by temporarily disabling critical services. The vulnerability also demonstrates poor input validation practices that could indicate broader security weaknesses within the application architecture. Security teams should consider this vulnerability in their risk assessment frameworks, particularly when evaluating the resilience of remote access infrastructure and the potential impact on business continuity operations.
Mitigation strategies should include immediate deployment of Fortinet's security patches and updates for all affected versions, ensuring that systems are updated to versions 7.2.5, 7.0.11, 6.4.13, 7.2.4, and 7.0.10 or later. Organizations should implement network segmentation and access controls to limit exposure of SSL VPN services to untrusted networks while monitoring for suspicious traffic patterns that may indicate exploitation attempts. Network administrators should configure intrusion detection systems to monitor for malformed bookmark parameter requests and establish automated alerting mechanisms. Additionally, implementing rate limiting and request validation controls at the network perimeter can help reduce the impact of potential exploitation attempts. Security teams should conduct comprehensive vulnerability assessments to identify any additional systems that may be affected by similar input validation issues, particularly within other network security appliances. The mitigation approach should align with NIST cybersecurity framework guidelines and incorporate continuous monitoring practices to detect and respond to potential exploitation attempts. Organizations should also review their incident response procedures to ensure preparedness for handling service disruption events related to this vulnerability, considering the potential for cascading effects on business operations and user productivity.