CVE-2016-8747 in Tomcat
Summary
by MITRE
An information disclosure issue was discovered in Apache Tomcat 8.5.7 to 8.5.9 and 9.0.0.M11 to 9.0.0.M15 in reverse-proxy configurations. Http11InputBuffer.java allows remote attackers to read data that was intended to be associated with a different request.
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Analysis
by VulDB Data Team • 10/15/2024
The vulnerability CVE-2016-8747 represents a critical information disclosure flaw in Apache Tomcat versions 8.5.7 through 8.5.9 and 9.0.0.M11 through 9.0.0.M15 when operating in reverse-proxy configurations. This issue stems from improper handling of HTTP request buffering mechanisms that can lead to cross-request data contamination. The flaw specifically affects the Http11InputBuffer.java component which manages the input buffer for HTTP requests, creating a scenario where data from one request can be inadvertently exposed to subsequent requests processed by the same connection. This vulnerability is particularly dangerous in environments where multiple clients share the same server connection or when requests are processed in a pipelined manner. The security implications extend beyond simple data leakage as this information disclosure can potentially expose sensitive session data, authentication tokens, or other confidential information that should remain isolated between individual client requests.
The technical root cause of this vulnerability lies in the improper synchronization and management of input buffers within the HTTP connector implementation. When Tomcat operates as a reverse proxy, it processes multiple requests over the same connection, and the buffer management logic fails to properly clear or reset buffer contents between requests. This allows data that was originally associated with one request to remain accessible when the buffer is reused for processing subsequent requests. The vulnerability manifests when the Http11InputBuffer.java component does not adequately sanitize buffer contents before reusing them for new request processing, creating a condition where remnants of previous request data can be read by the current request handler. This behavior violates fundamental security principles of request isolation and can be exploited by remote attackers who craft specific HTTP requests to trigger the buffer reuse scenario. The flaw is categorized under CWE-200 Information Exposure and aligns with ATT&CK technique T1005 Data from Local System, as it enables unauthorized access to data that should remain isolated between request contexts.
The operational impact of CVE-2016-8747 extends beyond simple information disclosure to potentially enable more sophisticated attacks including session hijacking, credential theft, and privilege escalation. In reverse-proxy configurations, where Tomcat serves as an intermediary between clients and backend servers, this vulnerability can be exploited to gain access to sensitive data that flows through the proxy. Attackers can leverage this flaw to read session identifiers, authentication credentials, or other confidential information that was processed in previous requests, effectively breaking the isolation between different client sessions. The vulnerability is particularly concerning in enterprise environments where Tomcat is commonly deployed as a reverse proxy for web applications, as it can compromise the security of entire application stacks. Organizations using affected versions of Tomcat in production environments face significant risk of data breaches and unauthorized access to sensitive information, especially when the reverse-proxy functionality is utilized for handling authenticated user requests or processing confidential data.
Mitigation strategies for CVE-2016-8747 require immediate deployment of patched versions of Apache Tomcat, specifically versions 8.5.10, 9.0.0.M16, or later releases that contain the necessary buffer management fixes. Organizations should prioritize upgrading their Tomcat installations to eliminate the risk of data leakage through buffer reuse scenarios. Additionally, administrators should implement network-level controls to restrict access to reverse-proxy configurations and monitor for unusual request patterns that might indicate exploitation attempts. The patch addresses the core buffer management issue by ensuring proper buffer clearing and reset operations between request processing cycles, preventing data contamination between requests. Security teams should also consider implementing additional monitoring controls to detect potential exploitation attempts, such as unusual request timing patterns or requests that might trigger buffer reuse conditions. Organizations should conduct comprehensive vulnerability assessments to identify all instances of affected Tomcat versions within their infrastructure and ensure that reverse-proxy configurations are properly secured through additional layers of authentication and authorization controls. The fix aligns with security best practices for maintaining request isolation and preventing cross-request data contamination in web server implementations.