CVE-2021-43063 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 6.4.0, version 6.3.15 and below, version 6.2.6 and below allows attacker to execute unauthorized code or commands via crafted HTTP GET requests to the login webpage.
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Analysis
by VulDB Data Team • 05/02/2025
This vulnerability represents a critical cross-site scripting flaw in Fortinet FortiWeb web application firewalls that affects multiple versions including 6.4.1 and 6.4.0, 6.3.15 and below, and 6.2.6 and below. The vulnerability stems from insufficient input validation and sanitization during web page generation processes, specifically when handling HTTP GET requests to the login webpage. Attackers can exploit this weakness by crafting malicious HTTP GET requests that contain malicious scripts, which then get executed in the context of other users' browsers. The flaw falls under CWE-79 which categorizes improper neutralization of input during web page generation as a primary cause of cross-site scripting vulnerabilities. This particular vulnerability operates at the application layer and specifically targets the authentication interface of the FortiWeb appliance, making it particularly dangerous as it could potentially allow attackers to hijack user sessions or escalate privileges.
The technical exploitation of this vulnerability occurs when the FortiWeb appliance fails to properly sanitize user-supplied input parameters in the login webpage. When an attacker submits a crafted HTTP GET request containing malicious payload through parameters such as username, password, or other input fields, the web application fails to neutralize the input before rendering it in the web page context. This allows the malicious script to execute in the browser of any user who views the affected page, potentially leading to session hijacking, credential theft, or unauthorized access to protected resources. The vulnerability demonstrates a classic XSS attack pattern where the malicious code is injected into the web application and then executed in the victim's browser context, creating a persistent threat vector that can be leveraged for further attacks.
The operational impact of this vulnerability is significant for organizations relying on FortiWeb for web application security protection. Since the vulnerability specifically targets the login webpage, it could allow attackers to bypass authentication mechanisms and gain unauthorized access to the web application firewall management interface. This creates a potential escalation path where an attacker could compromise the entire security infrastructure, as FortiWeb serves as a critical security component that protects web applications from various threats. The vulnerability could also enable attackers to establish persistent access through session hijacking, allowing them to maintain access even after initial exploitation attempts. The attack surface is particularly concerning because it affects multiple versions of the FortiWeb appliance, meaning organizations with older versions may be vulnerable even if they have patched other security issues.
Organizations should immediately implement mitigations including applying the latest Fortinet security patches and updates to address the vulnerability in affected versions. Network segmentation and monitoring should be enhanced to detect anomalous HTTP GET requests that may contain XSS payloads. Input validation and sanitization should be strengthened at the application level to prevent malicious content from being processed and rendered in web pages. Security teams should also conduct thorough vulnerability assessments to identify any potential exploitation attempts and implement web application firewalls or security monitoring tools that can detect and block suspicious requests. The vulnerability aligns with ATT&CK technique T1059.001 which involves command and scripting interpreter, as the XSS payload could potentially execute commands on the victim's browser or redirect them to malicious sites. Regular security awareness training for administrators is also recommended to recognize potential exploitation attempts and maintain vigilance against social engineering attacks that may leverage this vulnerability.