Source: cve@mitre.org
Cross-site scripting (XSS) vulnerability in the View Error Log functionality in Sun Java System Web Proxy Server 4.x before 4.0.6 allows remote attackers to inject arbitrary web script or HTML via unspecified vectors, aka BugID 6566246.
Sun Java System Web Proxy Server 4.x is vulnerable to a cross-site scripting (XSS) attack. This allows attackers to inject malicious scripts into the web proxy's error log, potentially leading to account compromise, data theft, or browser redirection for users accessing the proxy.
Step 1: Payload Delivery: An attacker crafts a malicious request to the vulnerable web proxy server, designed to trigger an error condition and write a payload to the error log. The payload is typically a JavaScript snippet or HTML tag designed to execute within a user's browser.
Step 2: Error Trigger: The crafted request causes an error within the web proxy server. This error, along with the attacker's payload, is then written to the error log.
Step 3: Log Access: An authenticated user, such as an administrator, accesses the 'View Error Log' functionality within the web proxy's administrative interface.
Step 4: Payload Execution: The web proxy server displays the contents of the error log, including the attacker's injected payload. Because the payload is not properly sanitized, it is rendered as HTML and executed by the user's browser.
The vulnerability stems from insufficient input validation and output encoding within the 'View Error Log' functionality. Specifically, the application fails to properly sanitize user-supplied input before displaying it within the error log. This allows an attacker to inject malicious JavaScript or HTML tags. When a user with access to the error log views the log, the injected script executes within their browser, leading to the XSS vulnerability. The root cause is a lack of proper input validation and output encoding (e.g., HTML entity encoding) of data written to the error log. The application trusts user-provided data without sanitization, leading to the execution of arbitrary code.
While no specific APT groups are directly linked to this CVE, XSS vulnerabilities are commonly used by various threat actors. The impact of successful exploitation (e.g., credential theft, session hijacking) makes it an attractive target. This CVE is not listed on the CISA KEV.
Monitor web proxy server logs for unusual error messages or patterns, especially those containing suspicious HTML or JavaScript code.
Analyze network traffic for requests containing potentially malicious payloads, such as JavaScript code or HTML tags, being sent to the web proxy server.
Implement a Web Application Firewall (WAF) to detect and block XSS attempts.
Review the web proxy server configuration for any unauthorized changes or modifications.
Upgrade to Sun Java System Web Proxy Server 4.0.6 or later.
Implement input validation to sanitize all user-supplied data before it is written to the error log.
Implement output encoding (e.g., HTML entity encoding) to escape special characters when displaying data from the error log.
Apply the principle of least privilege, restricting access to the 'View Error Log' functionality to only necessary personnel.
Regularly scan the web proxy server for vulnerabilities using vulnerability scanners.