CVE-2021-41015 in FortiWeb
Summary
by MITRE • 12/08/2021
A improper neutralization of input during web page generation ('cross-site scripting') in Fortinet FortiWeb version 6.4.1 and below, 6.3.15 and below allows attacker to execute unauthorized code or commands via crafted HTTP requests to SAML login handler
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Analysis
by VulDB Data Team • 05/02/2025
This vulnerability represents a critical cross-site scripting flaw in Fortinet FortiWeb appliances that affects versions 6.4.1 and earlier, as well as 6.3.15 and earlier. The vulnerability occurs within the SAML login handler component where user input is not properly sanitized during web page generation processes. Attackers can exploit this weakness by crafting malicious HTTP requests that inject malicious scripts into the SAML authentication flow, potentially compromising the security of the entire web application protection system. The vulnerability stems from insufficient input validation and output encoding mechanisms that fail to neutralize dangerous characters and script payloads before they are rendered in web responses.
The technical exploitation of this vulnerability leverages the fundamental principles of cross-site scripting attacks where malicious code injected into SAML login pages can execute in the context of authenticated users. When users interact with the compromised SAML handler, their browsers execute the injected scripts, potentially allowing attackers to steal session cookies, perform unauthorized actions, or redirect users to malicious sites. This vulnerability specifically targets the SAML authentication mechanism which is commonly used for single sign-on implementations, making it particularly dangerous as it can compromise enterprise authentication systems. The flaw exists in the web application firewall's handling of user-supplied data during the authentication process, where input validation occurs too late in the processing pipeline.
The operational impact of this vulnerability extends beyond simple script execution as it can lead to complete compromise of the FortiWeb appliance and the protected web applications. An attacker who successfully exploits this vulnerability can potentially escalate privileges, access sensitive configuration data, modify security policies, or use the appliance as a pivot point to attack internal network resources. The vulnerability affects organizations using FortiWeb for web application protection, particularly those implementing SAML-based authentication systems, which are common in enterprise environments. This weakness can result in significant data breaches, service disruption, and compliance violations that may trigger regulatory penalties and legal consequences.
Organizations should immediately implement mitigation strategies including applying the latest firmware updates from Fortinet that address this specific vulnerability. Network administrators should also consider implementing additional monitoring and detection measures to identify suspicious SAML authentication requests. The vulnerability aligns with CWE-79 which defines cross-site scripting flaws, and maps to ATT&CK technique T1190 for exploitation of vulnerabilities in web applications. Security teams should conduct comprehensive vulnerability assessments of their FortiWeb deployments and review SAML configuration settings to ensure proper input validation is implemented. Additionally, implementing web application firewalls with proper XSS protection mechanisms and conducting regular security testing of authentication handlers can help prevent exploitation of similar vulnerabilities in the future.