CVE-2021-32554 in Apport
Summary
by MITRE • 06/12/2021
It was discovered that read_file() in apport/hookutils.py would follow symbolic links or open FIFOs. When this function is used by the xorg package apport hooks, it could expose private data to other local users.
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Analysis
by VulDB Data Team • 06/14/2021
The vulnerability identified as CVE-2021-32554 resides within the apport debugging framework used by ubuntu systems to collect crash information and system data. This flaw specifically affects the read_file() function located in apport/hookutils.py which serves as a utility function for reading files during system crash reporting processes. The issue manifests when this function processes symbolic links or opens named pipes, creating a potential pathway for information disclosure that could compromise system security.
The technical flaw stems from insufficient validation within the read_file() function implementation. When processing files through apport hooks, particularly those associated with the xorg package responsible for graphics handling, the function fails to properly handle symbolic links and FIFOs. This behavior allows malicious local users to create symbolic links pointing to sensitive system files or named pipes that would otherwise be protected from direct access. The function's inability to distinguish between legitimate file access requests and potentially harmful symbolic link traversals creates an attack surface where unauthorized data exposure occurs.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable privilege escalation and lateral movement within affected systems. When the xorg package hooks utilize the vulnerable read_file() function, any local user can exploit this weakness to access private data that should remain restricted. This includes sensitive configuration files, authentication tokens, or other system-critical information that could be leveraged by attackers to gain deeper system access. The vulnerability particularly affects systems where apport is actively used for crash reporting and where the xorg graphics subsystem is present, making it a significant concern for desktop and server environments.
Mitigation strategies should focus on implementing proper file access validation within the read_file() function to prevent symbolic link traversal and FIFO opening operations. System administrators should ensure that affected packages are updated to versions that address this vulnerability through proper input validation and access control mechanisms. The fix typically involves modifying the function to explicitly check file types and reject symbolic links or FIFOs during file processing operations. Organizations should also consider implementing monitoring for suspicious file access patterns and ensure that apport configurations do not inadvertently expose sensitive system information. This vulnerability aligns with CWE-22 (Improper Limitation of a Pathname to a Restricted Directory) and may be categorized under ATT&CK technique T1005 (Data from Local System) for threat actors seeking to extract sensitive information from compromised systems.
The broader implications of this vulnerability highlight the importance of proper file access controls in system debugging and crash reporting frameworks. Security teams should review all file handling functions within system utilities to ensure they properly validate access requests and prevent unintended data exposure. Regular security audits of system components that handle file operations, particularly those used in automated reporting and debugging processes, are essential to prevent similar issues from emerging. This vulnerability demonstrates how seemingly benign utility functions can create significant security risks when proper access controls and input validation are not implemented, emphasizing the need for comprehensive security testing of all system components.