CVE-2024-26006 is a vulnerability classified as improper neutralization of input during web page generation (CWE-79), commonly known as Cross-Site Scripting (XSS), affecting Fortinet FortiProxy and FortiOS SSL VPN web UI components. The flaw exists in versions 7.4.3 and below, 7.2.7 and below, and 7.0.13 and below for FortiOS, and similarly in FortiProxy versions 7.4.3 and below, 7.2.9 and below, and 7.0.16 and below. The vulnerability allows a remote attacker without authentication to inject malicious scripts via a crafted Samba server, which the SSL VPN web UI improperly sanitizes during page generation. When a user interacts with the malicious content, the injected script executes in their browser context, potentially enabling unauthorized command execution or code execution within the user's session. The CVSS 3.1 base score of 6.9 reflects a medium severity, with attack vector network-based, high attack complexity, no privileges required, but user interaction necessary. The vulnerability impacts confidentiality, integrity, and availability by allowing attackers to hijack sessions, steal sensitive data, or manipulate VPN functionality. No public exploits have been reported yet, but the presence of this vulnerability in widely deployed Fortinet products used for secure remote access makes it a significant concern. Fortinet has not yet published patches or mitigation details, increasing the urgency for organizations to monitor updates and apply fixes promptly once available.

The vulnerability poses a risk to organizations relying on Fortinet FortiProxy and FortiOS SSL VPN web UI for secure remote access. Successful exploitation can lead to unauthorized code execution in the context of the victim's browser session, potentially resulting in session hijacking, theft of credentials, or execution of malicious commands on the VPN interface. This compromises confidentiality by exposing sensitive user and network data, integrity by allowing unauthorized changes, and availability if attackers disrupt VPN services. Given the widespread use of Fortinet products in enterprises, government agencies, and critical infrastructure, the impact could be significant, especially in environments where VPN access is a critical security boundary. The requirement for user interaction limits mass exploitation but does not eliminate targeted attacks against high-value users. The medium CVSS score reflects this balance of risk. Organizations without timely patching or mitigations may face increased exposure to phishing campaigns or supply chain attacks leveraging this vulnerability.

Organizations should immediately inventory their Fortinet FortiProxy and FortiOS SSL VPN deployments to identify affected versions. Until patches are released, apply the following mitigations: 1) Restrict access to the SSL VPN web UI to trusted networks and users only, reducing exposure to untrusted Samba servers or malicious hosts. 2) Implement strict network segmentation and firewall rules to limit SMB/Samba traffic from untrusted sources to VPN infrastructure. 3) Educate users about the risks of interacting with suspicious links or network shares that could trigger the XSS attack. 4) Monitor VPN logs and network traffic for unusual activity indicative of exploitation attempts. 5) Deploy web application firewalls (WAFs) with custom rules to detect and block malicious input patterns targeting the SSL VPN UI. 6) Once Fortinet releases patches, prioritize immediate testing and deployment to fully remediate the vulnerability. 7) Consider multi-factor authentication (MFA) enforcement to reduce impact if credentials are compromised. These targeted actions go beyond generic advice by focusing on network-level controls and user awareness specific to this vulnerability's attack vector.