Apache Tomcat Connectors Flaw Exposes Shared Memory to Local Attacks
Ubuntu security advisory USN-8369-1 details a vulnerability in Apache Tomcat Connectors where incorrect default permissions on Unix-like shared memory allow local attackers to access or modify mod_jk configuration data. The flaw poses risks of information disclosure and denial of service for affected deployments.
TL;DR
- Apache Tomcat Connectors uses overly permissive default shared memory permissions on Unix systems
- Local attackers can read or modify mod_jk configuration data stored in shared memory
- Exploitation could lead to sensitive information exposure or service disruption
- Affects systems running Tomcat with mod_jk connector on Unix-like platforms
- Patching and permission hardening are recommended for vulnerable installations
Ubuntu has released security notice USN-8369-1 addressing a privilege escalation and information disclosure vulnerability in Apache Tomcat Connectors. The issue stems from improper default permissions assigned to shared memory segments on Unix-like systems, creating an attack surface for local users.
Mod_jk, the Apache Tomcat connector module, stores configuration data in shared memory to facilitate communication between Apache HTTP Server and Tomcat application servers. When default permissions are too permissive, any local user on the system can potentially read sensitive configuration details or corrupt the shared memory segment.
This vulnerability underscores the importance of secure defaults in multi-user environments and highlights why system administrators must audit permission settings on shared resources, particularly in production deployments where Tomcat handles sensitive workloads.
Technical Details of the Vulnerability
- Apache Tomcat Connectors fail to enforce restrictive permissions on Unix shared memory segments by default
- Shared memory is used by mod_jk to store configuration and state information between Apache and Tomcat processes
- Local attackers with system access can read configuration data without authentication
- Attackers can also write to shared memory, potentially corrupting mod_jk state and triggering denial of service
- The flaw affects Unix-like systems including Linux distributions packaged by Ubuntu
Security Impact and Mitigation
- Sensitive information such as database credentials or internal URLs stored in mod_jk configuration may be exposed
- Denial of service is possible through shared memory corruption, disrupting Tomcat connector functionality
- Local privilege escalation scenarios may be chained with this vulnerability to amplify impact
- Organizations should apply the USN-8369-1 patch immediately to affected Ubuntu systems
- Manual permission hardening on shared memory segments (/dev/shm) provides temporary mitigation before patching
- Restrict local system access and follow principle of least privilege to reduce local attack surface
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