CVE-2011-2526 in Tomcat
Summary
by MITRE
Apache Tomcat 5.5.x before 5.5.34, 6.x before 6.0.33, and 7.x before 7.0.19, when sendfile is enabled for the HTTP APR or HTTP NIO connector, does not validate certain request attributes, which allows local users to bypass intended file access restrictions or cause a denial of service (infinite loop or JVM crash) by leveraging an untrusted web application.
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Analysis
by VulDB Data Team • 12/28/2024
The vulnerability identified as CVE-2011-2526 represents a critical security flaw in Apache Tomcat versions prior to specific patch releases, affecting the HTTP APR and HTTP NIO connectors when sendfile functionality is enabled. This issue stems from inadequate validation of request attributes within the web server's file handling mechanisms, creating potential attack vectors that could compromise system integrity and availability. The flaw specifically targets the interaction between the sendfile optimization feature and request attribute processing, where the server fails to properly validate the attributes of incoming requests before proceeding with file access operations. The vulnerability exists across multiple Tomcat version lines including 5.5.x, 6.x, and 7.x, indicating a widespread impact that affected numerous deployments in production environments.
The technical implementation of this vulnerability exploits the sendfile feature which is designed to optimize file delivery by allowing the operating system to transfer file data directly from disk to network sockets without copying data between user space and kernel space. When sendfile is enabled, Tomcat processes HTTP requests through the APR or NIO connectors and relies on specific request attributes to determine file access permissions and transfer parameters. However, the validation mechanism fails to properly examine these attributes, allowing malicious requests to manipulate the file access control parameters. Attackers can craft specially crafted requests that bypass intended access restrictions, potentially allowing them to read files outside of the web application's intended directory structure. The vulnerability also enables denial of service conditions through carefully constructed requests that can trigger infinite loops within the Tomcat processing logic or cause JVM crashes, effectively rendering the web server unavailable to legitimate users.
The operational impact of CVE-2011-2526 extends beyond simple access control bypass to encompass significant availability concerns that can affect business operations and system reliability. Organizations running affected Tomcat versions face potential data exposure risks where local attackers could access sensitive files that should be restricted to authorized users only. The denial of service component of this vulnerability creates additional operational challenges as system administrators must contend with potential service interruptions that could affect web application availability. From a compliance perspective, this vulnerability could result in violations of security standards such as those outlined in the CWE-20 standard for improper input validation, which specifically addresses weaknesses in software that fails to properly validate input data. The vulnerability also aligns with ATT&CK techniques related to privilege escalation and denial of service, as attackers can leverage this flaw to gain unauthorized access to system resources or disrupt service availability.
Mitigation strategies for CVE-2011-2526 primarily focus on upgrading to patched versions of Apache Tomcat where the sendfile validation has been corrected. Organizations should immediately implement version updates to Tomcat 5.5.34, 6.0.33, or 7.0.19 respectively, depending on their current deployment. Additionally, system administrators can disable the sendfile feature for affected connectors through configuration changes, though this may impact performance characteristics of file delivery operations. Security monitoring should include detection of suspicious request patterns that might indicate exploitation attempts, particularly focusing on unusual file access requests that could bypass normal access controls. Network-level protections such as firewalls and intrusion detection systems can be configured to monitor for patterns consistent with this vulnerability. The remediation process should also include comprehensive testing to ensure that the patched versions maintain application functionality while eliminating the security risks. Organizations should conduct thorough vulnerability assessments to identify all instances of affected Tomcat deployments and implement coordinated patching strategies to minimize operational disruption while maximizing security effectiveness.