CVE-2022-42469 in FortiGate
Summary
by MITRE • 04/11/2023
A permissive list of allowed inputs vulnerability [CWE-183] in FortiGate version 7.2.3 and below, version 7.0.9 and below Policy-based NGFW Mode may allow an authenticated SSL-VPN user to bypass the policy via bookmarks in the web portal.
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Analysis
by VulDB Data Team • 04/11/2023
This vulnerability exists within FortiGate's SSL-VPN implementation in Policy-based Next Generation Firewall mode where the system fails to properly validate input parameters when processing bookmarks within the web portal interface. The issue stems from a permissive input validation mechanism that does not adequately restrict or sanitize user-supplied data, creating an opportunity for authenticated attackers to manipulate the system's access control policies. The vulnerability specifically affects FortiGate versions 7.2.3 and below, as well as versions 7.0.9 and below, indicating a widespread exposure across multiple release branches of the security appliance.
The technical flaw manifests as a weakness in the input validation process where the system accepts certain bookmark parameters without proper sanitization or restriction checks. This allows an authenticated SSL-VPN user to craft malicious inputs that bypass intended policy enforcement mechanisms. The vulnerability operates at the application layer and leverages the existing authentication context to exploit a logic flaw in the policy evaluation engine. According to CWE-183, this represents a permissive list vulnerability where the system accepts inputs that should be rejected, creating a path for unauthorized access or privilege escalation. The flaw essentially allows an attacker to manipulate the web portal's bookmark functionality to gain access to resources or services that would normally be restricted by the firewall's policy rules.
The operational impact of this vulnerability is significant as it enables authenticated attackers to bypass security controls that are fundamental to the SSL-VPN's purpose of providing secure remote access. An attacker with valid SSL-VPN credentials can exploit this vulnerability to access internal network resources that should be restricted based on the firewall's policy configuration. This represents a critical compromise of the security model, as it allows lateral movement and potential access to sensitive internal systems. The vulnerability affects the core functionality of the Policy-based NGFW mode, which is designed to enforce granular access control policies, thereby undermining the entire security framework. The attack vector is particularly concerning because it requires only authentication credentials, making it accessible to users who have legitimate access to the SSL-VPN service but should not be able to bypass policy restrictions.
Mitigation strategies should focus on immediate patching of affected FortiGate versions to address the input validation flaw. Organizations should also implement network segmentation and additional monitoring to detect anomalous behavior in SSL-VPN sessions. The principle of least privilege should be enforced by limiting the scope of bookmarks and access rights granted to SSL-VPN users. Security teams should conduct thorough audits of SSL-VPN configurations and policy enforcement mechanisms to identify potential exploitation vectors. Additionally, implementing behavioral analytics and anomaly detection systems can help identify unusual access patterns that may indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1078.004 which covers valid accounts and T1566 which covers credential harvesting, making it a critical concern for organizations that rely on SSL-VPN for remote access security.