CVE-2016-4847 in Web UI
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in site/search.php in OSSEC Web UI before 0.9 allows remote attackers to inject arbitrary web script or HTML by leveraging an unanchored regex.
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Analysis
by VulDB Data Team • 12/01/2022
The CVE-2016-4847 vulnerability represents a critical cross-site scripting flaw within the OSSEC Web UI's search functionality, specifically in the site/search.php component. This vulnerability affects versions prior to 0.9 of the OSSEC security information and event management platform, which is widely used for intrusion detection and security monitoring across enterprise environments. The flaw exists in the web user interface's handling of search parameters, creating a persistent security risk that can be exploited by remote attackers without requiring authentication or privileged access. The vulnerability's impact extends beyond simple data theft, as it can enable attackers to execute malicious scripts within the context of authenticated users' browsers, potentially leading to complete session hijacking or data exfiltration.
The technical root cause of this vulnerability stems from improper input validation and sanitization within the search.php script. Attackers can exploit an unanchored regular expression pattern that fails to properly sanitize user-supplied input before incorporating it into the web page response. This unanchored regex allows malicious payloads to be injected at any point within the search query parameter, bypassing standard security filters that might only check for specific patterns at the beginning or end of input strings. The vulnerability specifically manifests when the OSSEC Web UI processes search terms containing malicious script code, which then gets reflected back to users without appropriate HTML escaping or encoding mechanisms. This flaw directly maps to CWE-79, which defines the common weakness of cross-site scripting vulnerabilities where untrusted data is improperly incorporated into web page content.
The operational impact of CVE-2016-4847 extends significantly beyond simple script injection, as it creates multiple attack vectors that can be leveraged by threat actors in sophisticated campaigns. An attacker who successfully exploits this vulnerability can execute arbitrary JavaScript code within the context of any authenticated user's browser session, potentially leading to session hijacking, credential theft, or redirection to malicious sites. The vulnerability's remote nature means that attackers can exploit it from anywhere on the internet without requiring physical access to the network or system. Given that OSSEC Web UI is commonly deployed in security-sensitive environments where administrators regularly access the interface, the potential for privilege escalation exists when attackers can inject scripts that manipulate the web interface's behavior or access administrative functions. This vulnerability also aligns with ATT&CK technique T1059.007 for Scripting, where adversaries leverage web-based scripting languages to execute malicious code on victim systems.
Organizations utilizing OSSEC Web UI should prioritize immediate remediation through version updates to 0.9 or later, which contain proper input validation and sanitization measures. The fix typically involves implementing proper HTML escaping for all user-supplied input, utilizing anchored regular expressions for validation, and employing content security policies to prevent unauthorized script execution. Security teams should also implement network-based detection measures to monitor for suspicious search parameter patterns that might indicate exploitation attempts. Additional mitigations include restricting direct internet access to the OSSEC Web UI through firewall rules, implementing web application firewalls, and conducting regular security assessments of the web interface to identify similar vulnerabilities. The vulnerability serves as a reminder of the importance of proper input validation and output encoding in web applications, particularly in security tools where the web interface may be exposed to untrusted users or attackers. Organizations should also consider implementing automated security scanning tools that can detect similar regex-based vulnerabilities in their web applications, as the unanchored regex pattern is a common indicator of potential XSS vulnerabilities that can be exploited in various web frameworks and applications.