CVE-2007-6286 in Tomcat
Summary
by MITRE
Apache Tomcat 5.5.11 through 5.5.25 and 6.0.0 through 6.0.15, when the native APR connector is used, does not properly handle an empty request to the SSL port, which allows remote attackers to trigger handling of "a duplicate copy of one of the recent requests," as demonstrated by using netcat to send the empty request.
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Analysis
by VulDB Data Team • 08/06/2019
The vulnerability identified as CVE-2007-6286 represents a critical flaw in Apache Tomcat versions ranging from 5.5.11 through 5.5.25 and 6.0.0 through 6.0.15 when utilizing the native APR connector for SSL connections. This issue stems from improper handling of empty requests directed to SSL ports, creating a condition where attackers can manipulate the request processing pipeline to trigger duplicate request handling. The vulnerability specifically manifests when the APR connector is enabled, which provides native operating system-level optimizations for network I/O operations and SSL processing. The flaw enables remote attackers to exploit a race condition or processing anomaly that results in the server incorrectly managing request flow and potentially executing duplicate requests that were recently processed.
The technical mechanism behind this vulnerability involves the APR connector's SSL request handling logic failing to properly validate or process empty requests sent to SSL ports. When an empty request is received, the system does not adequately distinguish between legitimate empty requests and maliciously crafted ones, leading to a scenario where the server maintains a reference to a previous request and attempts to process a duplicate copy. This behavior creates a potential for request replay attacks and can be exploited through simple network tools like netcat to send empty requests to the SSL port. The vulnerability is particularly concerning because it operates at the protocol level where SSL connections are established, potentially allowing attackers to manipulate the request processing sequence and execute unintended operations.
From an operational impact perspective, this vulnerability creates significant security risks for organizations relying on Apache Tomcat with APR connector configurations for SSL services. Attackers can exploit this flaw to potentially execute duplicate requests, which may lead to unintended business logic execution, data processing anomalies, or even authentication bypass scenarios depending on the application's implementation. The vulnerability's remote exploitability means that attackers do not require local system access or authentication credentials to trigger the condition, making it particularly dangerous for publicly exposed web services. The issue can also contribute to denial of service conditions if the duplicate request processing causes system resource exhaustion or application instability.
The vulnerability aligns with CWE-129, which addresses improper handling of input validation, and can be categorized under ATT&CK technique T1190 for exploitation of remote services. Organizations should immediately implement mitigations including updating to patched versions of Apache Tomcat, disabling the APR connector if not required for performance reasons, or implementing network-level controls to filter empty requests to SSL ports. The recommended approach involves upgrading to versions beyond the affected ranges, typically Tomcat 5.5.26 and 6.0.16, which contain the necessary patches to properly handle empty requests and prevent the duplicate request processing behavior. Additionally, network segmentation and monitoring of SSL port traffic can help detect and prevent exploitation attempts, while application-level request validation can provide additional defense-in-depth measures against similar vulnerabilities.