CVE-2016-9459 in ownCloud Server
Summary
by MITRE
Nextcloud Server before 9.0.52 & ownCloud Server before 9.0.4 are vulnerable to a log pollution vulnerability potentially leading to a local XSS. The download log functionality in the admin screen is delivering the log in JSON format to the end-user. The file was delivered with an attachment disposition forcing the browser to download the document. However, Firefox running on Microsoft Windows would offer the user to open the data in the browser as an HTML document. Thus any injected data in the log would be executed.
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Analysis
by VulDB Data Team • 11/22/2022
The vulnerability identified as CVE-2016-9459 represents a significant security flaw in Nextcloud Server versions prior to 9.0.52 and ownCloud Server versions prior to 9.0.4. This issue stems from improper handling of log file delivery mechanisms within the administrative interface, creating a vector for cross-site scripting attacks through log pollution. The vulnerability specifically affects the download log functionality that administrators use to access system logs for troubleshooting and monitoring purposes. When users attempt to download log files through the admin screen, the system delivers the content in JSON format but fails to properly enforce content disposition headers that would prevent browser interpretation of the downloaded data.
The technical exploitation of this vulnerability occurs due to inconsistent browser behavior, particularly with Firefox running on Microsoft Windows operating systems. While the system attempts to deliver the log file with attachment disposition headers that should force browser download, Firefox exhibits different behavior by offering users the option to open the JSON data directly in the browser as an HTML document. This inconsistency creates a pathway for malicious actors to inject JavaScript code into the log files, which then executes when the browser attempts to render the content. The vulnerability is classified under CWE-79 as a cross-site scripting issue, specifically involving the improper handling of user-provided data within a web application context.
The operational impact of this vulnerability extends beyond simple XSS execution, as it provides attackers with potential access to administrative functions and sensitive system information. When attackers successfully inject malicious code into the log files, they can execute arbitrary scripts in the context of the victim's browser session, potentially gaining access to administrative privileges or sensitive data. The vulnerability affects the integrity of system logging mechanisms, which are critical for security monitoring and incident response. Attackers can exploit this by injecting malicious payloads into log entries, which then execute when administrators view the logs, creating a persistent threat vector that can be difficult to detect and remediate. This vulnerability aligns with ATT&CK technique T1070.004 which covers "Indicator Removal on Host: File Deletion" and T1213.002 which addresses "Data from Information Repositories: Databases."
Mitigation strategies for this vulnerability require immediate patching of affected systems to versions 9.0.52 for Nextcloud and 9.0.4 for ownCloud, which contain the necessary fixes for proper content disposition handling. Organizations should also implement additional security measures such as regular log file monitoring and validation to detect potential injection attempts, proper input sanitization for log entries, and enforcement of strict content security policies. The fix addresses the core issue by ensuring that log files are properly delivered with appropriate headers that prevent browsers from interpreting the content as executable HTML, regardless of browser implementation differences. System administrators should also consider implementing web application firewalls to monitor and block suspicious log file access patterns, and establish regular security audits of logging mechanisms to prevent similar vulnerabilities from emerging in other components of the application stack.