CVE-2011-3585 in Samba
Summary
by MITRE
Multiple race conditions in the (1) mount.cifs and (2) umount.cifs programs in Samba 3.6 allow local users to cause a denial of service (mounting outage) via a SIGKILL signal during a time window when the /etc/mtab~ file exists.
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Analysis
by VulDB Data Team • 04/22/2023
The vulnerability described in CVE-2011-3585 represents a critical race condition flaw affecting Samba 3.6's mount.cifs and umount.cifs utilities. This issue stems from improper handling of file system operations during the mounting and unmounting processes, creating exploitable time windows where system stability is compromised. The vulnerability specifically targets the /etc/mtab~ file which serves as a temporary backup file during mount operations, making it a critical point of failure in the system's file system management infrastructure.
The technical implementation of this vulnerability exploits a fundamental timing issue within the Samba suite's file system management utilities. During the execution of mount.cifs or umount.cifs operations, there exists a narrow time window when the /etc/mtab~ file is present in the filesystem. If a SIGKILL signal is delivered to the process during this critical period, the system enters an inconsistent state that results in a complete denial of service for mounting operations. This race condition occurs because the programs fail to properly synchronize their file system modifications with signal handling mechanisms, creating a scenario where process termination interrupts critical file operations.
From an operational perspective, this vulnerability poses significant risks to enterprise environments that rely on Samba for file sharing and network access. The denial of service condition affects mounting capabilities across the entire system, potentially disrupting network file access for multiple users and applications simultaneously. Attackers can exploit this weakness by simply sending SIGKILL signals to the affected processes during their execution windows, requiring minimal privileges and technical expertise to execute successful attacks. The impact extends beyond simple service interruption as it can cascade into broader system stability issues affecting other network services that depend on proper file system state management.
The vulnerability aligns with CWE-362, which specifically addresses race conditions in concurrent programming environments, and demonstrates how improper synchronization can lead to system instability. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and denial of service operations, as local users can leverage it to disrupt system services without requiring elevated privileges. The attack vector is particularly concerning because it requires no special permissions beyond local access to the system, making it an attractive target for malicious actors seeking to disrupt network services. Organizations should implement immediate mitigations including updating to patched versions of Samba, implementing proper signal handling in custom scripts, and monitoring for abnormal process termination during mount operations.
Security practitioners should note that this vulnerability represents a classic example of how seemingly simple file system operations can become complex concurrency issues when not properly managed. The flaw demonstrates the critical importance of proper synchronization mechanisms in system utilities and highlights the need for comprehensive testing of file system operations under various conditions. Organizations should also consider implementing process monitoring and alerting systems to detect unusual SIGKILL signal patterns that might indicate exploitation attempts. The remediation approach should focus on both immediate patching and long-term architectural improvements to ensure proper signal handling and file system consistency during critical operations.