CVE-2015-6508 in pfSense
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in pfSense before 2.2.3 allows remote attackers to inject arbitrary web script or HTML via the descr parameter in a "new" action to system_authservers.php.
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Analysis
by VulDB Data Team • 06/12/2022
The CVE-2015-6508 vulnerability represents a critical cross-site scripting flaw discovered in pfSense firewall software versions prior to 2.2.3. This vulnerability resides within the system_authservers.php script which handles authentication server management functionality. The flaw specifically affects the handling of the descr parameter when processing a "new" action, creating an avenue for remote attackers to execute malicious web scripts or HTML code within the context of authenticated user sessions. The vulnerability stems from inadequate input validation and output encoding practices within the web application's user interface components.
The technical exploitation of this vulnerability follows a classic XSS attack pattern where malicious input is accepted through the descr parameter without proper sanitization. When the pfSense web interface processes this parameter during authentication server creation, it fails to properly encode or escape special characters that could be interpreted as HTML or JavaScript code. Attackers can craft malicious payloads that, when submitted through the affected parameter, get executed in the browsers of legitimate users who view the affected pages. This creates a persistent threat vector where attackers can steal session cookies, perform actions on behalf of users, or redirect them to malicious sites.
The operational impact of this vulnerability extends beyond simple script injection, as it represents a significant compromise of the web application's security model. An attacker with remote access capabilities can leverage this vulnerability to escalate privileges within the pfSense management interface, potentially gaining full administrative control over the firewall. The vulnerability affects all users who have access to the authentication server management functionality, making it particularly dangerous in environments where multiple administrators interact with the system. This flaw directly violates the principle of least privilege and undermines the integrity of the authentication system.
Mitigation strategies for CVE-2015-6508 should prioritize immediate software updates to pfSense version 2.2.3 or later, which contain the necessary patches to address the input validation deficiencies. Organizations should implement additional defensive measures including web application firewalls that can detect and block suspicious parameter values, input sanitization at multiple layers, and comprehensive monitoring of authentication server management activities. The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws, and maps to ATT&CK technique T1059.007 for script injection. Security teams should conduct thorough penetration testing to verify that all affected parameters are properly sanitized and implement automated vulnerability scanning to detect similar issues in other web applications within the network infrastructure.