CVE-2016-9774 in Tomcat
Summary
by MITRE
The postinst script in the tomcat6 package before 6.0.45+dfsg-1~deb7u4 on Debian wheezy, before 6.0.35-1ubuntu3.9 on Ubuntu 12.04 LTS and on Ubuntu 14.04 LTS; the tomcat7 package before 7.0.28-4+deb7u8 on Debian wheezy, before 7.0.56-3+deb8u6 on Debian jessie, before 7.0.52-1ubuntu0.8 on Ubuntu 14.04 LTS, and on Ubuntu 12.04 LTS, 16.04 LTS, and 16.10; and the tomcat8 package before 8.0.14-1+deb8u5 on Debian jessie, before 8.0.32-1ubuntu1.3 on Ubuntu 16.04 LTS, before 8.0.37-1ubuntu0.1 on Ubuntu 16.10, and before 8.0.38-2ubuntu1 on Ubuntu 17.04 might allow local users with access to the tomcat account to obtain sensitive information or gain root privileges via a symlink attack on the Catalina localhost directory.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 11/14/2022
The vulnerability identified as CVE-2016-9774 represents a critical privilege escalation and information disclosure issue affecting multiple versions of Apache Tomcat packages across various Debian and Ubuntu distributions. This flaw resides within the postinst script of the tomcat6, tomcat7, and tomcat8 packages, where improper handling of symbolic links during the package installation process creates exploitable conditions for local attackers with access to the tomcat user account. The vulnerability specifically targets the Catalina localhost directory, which serves as the primary deployment location for web applications in Apache Tomcat environments, making it a prime target for privilege escalation attacks.
The technical implementation of this vulnerability stems from a symlink attack that exploits the insecure creation of directory structures during package installation. When the postinst script executes, it processes the Catalina localhost directory without properly validating or sanitizing symbolic link references that may have been established by the tomcat user. This allows an attacker with tomcat account access to create malicious symbolic links that point to sensitive system files or directories, effectively enabling information disclosure when the installation process attempts to create or modify the targeted locations. The flaw operates under CWE-377, which specifically addresses insecure temporary file handling and symlink attacks, and aligns with ATT&CK technique T1068 for local privilege escalation through insecure file permissions and symbolic link manipulation.
The operational impact of this vulnerability extends beyond simple information disclosure to encompass full system compromise when attackers leverage the privilege escalation capabilities. An attacker with access to the tomcat user account can manipulate the installation process to gain root privileges, effectively bypassing the standard security boundaries that separate the web application runtime from the underlying operating system. This creates a scenario where local users can escalate their privileges to root level, potentially leading to complete system compromise and unauthorized access to all system resources, databases, and sensitive information stored on the host. The vulnerability affects multiple LTS versions of Ubuntu and Debian, indicating a widespread exposure across long-term support distributions that are commonly used in enterprise environments and production systems.
Mitigation strategies for CVE-2016-9774 require immediate patching of affected tomcat packages to versions that properly handle symbolic link conditions during installation processes. Organizations should ensure that all systems running affected tomcat versions are updated to the patched releases, specifically targeting the version numbers mentioned in the vulnerability description for each respective distribution. Additional defensive measures include implementing proper file system permissions and access controls for the tomcat user account, monitoring for unauthorized symbolic link creation in tomcat directories, and conducting regular security audits to identify potential exploitation attempts. Security teams should also consider implementing process monitoring for installation scripts and privilege escalation activities, as well as establishing network segmentation to limit the potential impact of successful exploitation attempts. The vulnerability demonstrates the critical importance of secure package installation processes and proper privilege management in preventing local privilege escalation attacks that can compromise entire system infrastructures.