CVE-2017-3125 in FortiMail
Summary
by MITRE
An unauthenticated XSS vulnerability with FortiMail 5.0.0 - 5.2.9 and 5.3.0 - 5.3.8 could allow an attacker to execute arbitrary scripts in the security context of the browser of a victim logged in FortiMail, assuming the victim is social engineered into clicking an URL crafted by the attacker.
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Analysis
by VulDB Data Team • 08/29/2020
This vulnerability represents a critical cross-site scripting flaw in FortiMail email security appliances that affects versions 5.0.0 through 5.2.9 and 5.3.0 through 5.3.8. The vulnerability stems from insufficient input validation and output encoding mechanisms within the web interface of the FortiMail system, allowing attackers to inject malicious JavaScript code through specially crafted URLs. The flaw exists in the authentication handling mechanism where the system fails to properly sanitize user-supplied input parameters before rendering them in web responses. This creates an opportunity for attackers to exploit the vulnerability without requiring valid credentials, making it particularly dangerous in enterprise environments where administrators regularly interact with the web interface.
The technical implementation of this vulnerability occurs when the FortiMail web application processes user input through URL parameters or form fields without adequate sanitization. When a victim administrator clicks on a maliciously crafted URL containing XSS payloads, the injected scripts execute within the victim's browser session with the privileges of the logged-in user. This allows attackers to perform actions such as stealing session cookies, modifying email configurations, accessing sensitive administrative functions, or redirecting users to malicious sites. The vulnerability aligns with CWE-79 which describes cross-site scripting flaws where untrusted data is improperly integrated into web pages without proper validation or encoding. The attack vector specifically leverages social engineering techniques to trick administrators into clicking malicious links, making it particularly challenging to defend against through traditional network security measures.
The operational impact of this vulnerability extends beyond simple script execution as it provides attackers with elevated privileges within the email security infrastructure. Administrators who are logged into the FortiMail web interface become potential victims, creating a direct pathway for attackers to compromise the entire email security ecosystem. This vulnerability can be exploited to manipulate email filtering rules, access email archives, modify user accounts, or even exfiltrate sensitive data through the compromised administrative session. The risk is amplified because FortiMail appliances often serve as critical security gateways in enterprise environments, making successful exploitation potentially devastating for organizational email security. This type of vulnerability also aligns with ATT&CK technique T1059 which covers execution through command and scripting interpreters, as the injected scripts can leverage legitimate administrative functions to perform malicious activities.
Mitigation strategies should focus on immediate patch application to versions that address the input validation deficiencies, combined with network-level protections such as web application firewalls that can detect and block suspicious XSS patterns. Organizations should implement strict input validation policies and output encoding mechanisms throughout the web application stack. Regular security awareness training for administrators can help reduce the risk of successful social engineering attacks that exploit this vulnerability. Network segmentation and monitoring of web application traffic can provide early detection of exploitation attempts. The vulnerability demonstrates the importance of secure coding practices and input sanitization, particularly for web interfaces that handle administrative functions. Additionally, implementing Content Security Policy headers and regular security assessments can help prevent similar issues in other components of the email security infrastructure.