CVE-2018-1121 in procps
Summary
by MITRE
procps-ng, procps is vulnerable to a process hiding through race condition. Since the kernel's proc_pid_readdir() returns PID entries in ascending numeric order, a process occupying a high PID can use inotify events to determine when the process list is being scanned, and fork/exec to obtain a lower PID, thus avoiding enumeration. An unprivileged attacker can hide a process from procps-ng's utilities by exploiting a race condition in reading /proc/PID entries. This vulnerability affects procps and procps-ng up to version 3.3.15, newer versions might be affected also.
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Analysis
by VulDB Data Team • 12/09/2024
The vulnerability described in CVE-2018-1121 represents a sophisticated race condition attack vector that exploits the fundamental design of the Linux /proc filesystem interface. This flaw specifically targets procps-ng and procps utilities, which are widely used for system monitoring and process management across Unix-like operating systems. The vulnerability stems from the predictable ordering behavior of kernel functions that enumerate process information, creating a window of opportunity for malicious processes to manipulate their visibility within system monitoring tools.
The technical implementation of this vulnerability relies on the kernel's proc_pid_readdir() function, which consistently returns process identifier entries in ascending numeric order. This deterministic behavior creates a exploitable timing window where a process can monitor inotify events to detect when the system is scanning the /proc filesystem for process listings. When such scanning activity is detected, the vulnerable process can immediately fork and execute itself with a lower process identifier, effectively moving to a position where it will be processed before the scanning routine completes its enumeration. This manipulation allows the process to avoid detection by utilities like ps, top, and other procps-ng tools that rely on sequential scanning of /proc entries.
The operational impact of this vulnerability extends beyond simple process hiding to represent a significant security concern for system administrators and security monitoring systems. Unprivileged attackers can leverage this race condition to conceal malicious processes from routine system checks, potentially evading detection by security tools that depend on process enumeration for threat identification. The vulnerability affects versions of procps-ng up to 3.3.15, though newer versions may also be susceptible, making this a persistent threat that requires careful consideration of system monitoring strategies. This type of attack directly violates the principle of least privilege by allowing processes to manipulate their own visibility within system monitoring interfaces, creating a false sense of system security.
The vulnerability aligns with several cybersecurity frameworks and attack patterns, including CWE-362 which categorizes race conditions as a fundamental security weakness, and ATT&CK technique T1057 for process discovery and T1063 for credential dumping. The attack methodology follows the pattern of privilege escalation through process manipulation, where a low-privilege user can effectively bypass system monitoring controls. From a compliance perspective, this vulnerability could impact systems under regulatory frameworks such as PCI DSS, HIPAA, and SOX that require comprehensive system monitoring and audit capabilities. Organizations implementing security information and event management systems must consider this vulnerability as a potential bypass mechanism for detecting malicious activity.
Mitigation strategies for CVE-2018-1121 should focus on both immediate system updates and architectural improvements to process enumeration mechanisms. The primary recommendation involves upgrading to procps-ng versions that have addressed this race condition, with administrators verifying that their systems are running patched versions. Additional protective measures include implementing more robust process monitoring solutions that utilize kernel-level interfaces rather than relying solely on /proc filesystem enumeration, deploying process integrity checking mechanisms, and establishing baseline process states for comparison. System administrators should also consider implementing monitoring for inotify events related to /proc filesystem access patterns, as these could indicate attempts to exploit the race condition. The vulnerability highlights the importance of designing system monitoring tools with awareness of potential timing attacks and the need for more sophisticated process enumeration methods that do not rely on predictable ordering behaviors.