CVE-2022-47952 in lxc
Summary
by MITRE • 01/01/2023
lxc-user-nic in lxc through 5.0.1 is installed setuid root, and may allow local users to infer whether any file exists, even within a protected directory tree, because "Failed to open" often indicates that a file does not exist, whereas "does not refer to a network namespace path" often indicates that a file exists. NOTE: this is different from CVE-2018-6556 because the CVE-2018-6556 fix design was based on the premise that "we will report back to the user that the open() failed but the user has no way of knowing why it failed"; however, in many realistic cases, there are no plausible reasons for failing except that the file does not exist.
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Analysis
by VulDB Data Team • 04/11/2025
The vulnerability described in CVE-2022-47952 affects the lxc-user-nic utility within the Linux Containers (LXC) project, specifically versions through 5.0.1. This utility is installed with setuid root permissions, making it a critical component that requires careful security analysis. The flaw stems from the utility's handling of file access operations and its inconsistent error messaging behavior when attempting to access network namespace paths. The vulnerability represents a classic information disclosure issue that can be exploited to perform reconnaissance activities within containerized environments.
The technical implementation of this vulnerability lies in how lxc-user-nic processes file access attempts through its setuid execution context. When the utility encounters a file access operation, it provides different error messages depending on whether the file exists or not. Specifically, when a file does not exist, the system reports "Failed to open" messages, while existing files trigger "does not refer to a network namespace path" error messages. This differential reporting creates a timing-based information leakage mechanism that allows local attackers to determine file existence without direct access to those files. The vulnerability operates at the kernel interface level where file system operations are processed through the setuid binary.
The operational impact of this vulnerability extends beyond simple file enumeration, as it provides attackers with a method to map directory structures and identify protected files within containerized environments. This information disclosure can be leveraged to understand system architecture and potentially identify additional attack vectors. The vulnerability is particularly concerning in containerized deployments where multiple users share the same host system, as it allows local users to perform reconnaissance without elevated privileges. This behavior can be exploited to gather intelligence about running containers, their configurations, and potentially identify other vulnerabilities within the container ecosystem.
From a cybersecurity perspective, this vulnerability aligns with CWE-200 (Information Exposure) and demonstrates characteristics similar to those found in ATT&CK technique T1083 (File and Directory Discovery) and T1592 (Pre-Attack). The inconsistent error handling creates a side-channel attack vector that can be used for reconnaissance purposes, making it a valuable asset for threat actors planning more sophisticated attacks. The vulnerability's classification as a local information disclosure issue means that it can be exploited by any user with access to the system, potentially allowing for privilege escalation or further attack planning. Security professionals should consider this vulnerability when assessing container security postures and implementing defense-in-depth strategies.
The fix for this vulnerability requires modifications to how lxc-user-nic handles file access operations and error reporting to ensure consistent behavior regardless of file existence. System administrators should immediately update to versions of LXC that contain the patched implementation, as the setuid nature of the utility makes it a high-value target for exploitation. Organizations running containerized workloads should also implement monitoring for unusual file access patterns that might indicate exploitation attempts. The vulnerability underscores the importance of careful error handling in setuid applications and the need for security reviews of privileged utilities that interact with file systems.