CVE-2015-4029 in pfSense
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the WebGUI in pfSense before 2.2.3 allows remote attackers to inject arbitrary web script or HTML via the zone parameter in a del action to services_captiveportal_zones.php.
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Analysis
by VulDB Data Team • 10/18/2017
The vulnerability CVE-2015-4029 represents a critical cross-site scripting flaw located within the WebGUI interface of pfSense firewall software versions prior to 2.2.3. This issue specifically affects the captive portal functionality where user input is not properly sanitized before being rendered back to the browser. The vulnerability exists in the services_captiveportal_zones.php script which processes zone parameters during delete operations, creating an avenue for malicious actors to execute arbitrary web scripts or HTML code within the context of other users' browsers.
The technical exploitation of this vulnerability occurs through a carefully crafted HTTP request that targets the del action within the captive portal zones management interface. When an attacker submits a malicious zone parameter containing script code, the vulnerable pfSense WebGUI fails to adequately validate or escape this input before incorporating it into dynamically generated HTML responses. This failure in input sanitization creates a persistent XSS vector that can be leveraged by remote attackers without requiring authentication or prior access to the system. The vulnerability falls under CWE-79 which specifically addresses cross-site scripting flaws, and aligns with ATT&CK technique T1566.001 related to spearphishing attachments.
The operational impact of this vulnerability extends beyond simple script execution as it can enable attackers to hijack user sessions, steal authentication credentials, modify web content, or redirect users to malicious websites. An attacker could potentially escalate the attack by crafting payloads that exploit the captive portal's administrative interface, potentially gaining unauthorized access to the firewall's configuration settings. The vulnerability particularly affects organizations relying on pfSense for network access control, as captive portal functionality is commonly used for guest network access, employee authentication, and network security enforcement. The remote nature of the attack means that exploitation can occur from anywhere on the internet without requiring physical access to the network infrastructure.
Mitigation strategies for this vulnerability include immediate upgrading to pfSense version 2.2.3 or later where the input validation has been properly implemented. Network administrators should also implement additional security measures such as web application firewalls that can detect and block malicious payloads targeting known XSS patterns. Regular security assessments and input validation reviews should be conducted to identify similar vulnerabilities in other components of the network infrastructure. The remediation process should include comprehensive testing to ensure that all user-supplied inputs are properly sanitized before being processed by the WebGUI, implementing proper output encoding, and maintaining up-to-date security patches for all network security appliances. Organizations should also consider implementing security monitoring solutions that can detect unusual traffic patterns or attempts to exploit known vulnerabilities in their network infrastructure.