CVE-2019-6146 in Web Security
Summary
by MITRE
It has been reported that cross-site scripting (XSS) is possible in Forcepoint Web Security, version 8.x, via host header injection. CVSSv3.0: 5.3 (Medium) (/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N)
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Analysis
by VulDB Data Team • 06/15/2025
The vulnerability identified as CVE-2019-6146 represents a critical cross-site scripting flaw within Forcepoint Web Security version 8.x systems, specifically exploitable through host header injection techniques. This vulnerability resides in the web application's handling of HTTP host headers during request processing, creating an avenue for malicious actors to inject malicious scripts into web responses. The issue manifests when the application fails to properly sanitize or validate host header values before incorporating them into dynamic web content, potentially allowing attackers to manipulate the application's behavior and execute unauthorized code within users' browsers.
The technical exploitation of this vulnerability follows a well-established pattern within the realm of web application security where host header injection serves as a precursor to XSS attacks. When an application processes HTTP requests and uses host header values without proper validation, attackers can manipulate these headers to inject malicious JavaScript payloads. This particular flaw falls under the Common Weakness Enumeration category CWE-79, which specifically addresses cross-site scripting vulnerabilities, and more broadly under CWE-20, which encompasses improper input validation. The vulnerability's medium severity rating of 5.3 on the CVSSv3.0 scale reflects the limited attack surface and the requirement for an attacker to first gain access to the host header injection capability before executing the XSS payload.
The operational impact of this vulnerability extends beyond simple script execution, potentially enabling attackers to perform session hijacking, steal sensitive user information, or redirect users to malicious websites. Since the vulnerability affects the web security appliance itself, it could compromise the very security mechanisms designed to protect network traffic, creating a dangerous scenario where an attacker could bypass security controls and execute malicious code within the context of a victim's browser session. The attack vector requires network access to the vulnerable web interface and does not necessarily require authentication, making it particularly concerning for organizations relying on Forcepoint Web Security for their network protection. This vulnerability could be exploited in conjunction with other attack techniques, potentially allowing for privilege escalation or lateral movement within a network environment.
Mitigation strategies for CVE-2019-6146 should focus on immediate patching of the Forcepoint Web Security appliances to the latest available versions that address the host header injection vulnerability. Organizations should implement proper input validation and sanitization mechanisms to ensure that all host header values are properly validated before being processed or incorporated into web responses. Network administrators should consider implementing additional security controls such as web application firewalls that can detect and block malicious host header values, and regular security assessments should be conducted to identify similar vulnerabilities in other web applications. The remediation process should also include monitoring network traffic for suspicious host header values and implementing proper logging mechanisms to track potential exploitation attempts. Organizations should follow the ATT&CK framework's guidance for defending against web application attacks by implementing proper input validation controls and ensuring that all web applications properly handle user-supplied data to prevent XSS vulnerabilities.