CVE-2021-32551 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 openjdk-15 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-2021-32551 resides within the apport package's hookutils.py module, specifically in the read_file() function implementation. This flaw represents a significant security weakness that enables unauthorized data exposure through improper handling of symbolic links and named pipes. The issue manifests when the read_file() function processes files that are symbolic links or FIFOs, allowing malicious local users to potentially access sensitive information that should remain restricted. The vulnerability is particularly concerning because it affects the openjdk-15 package's apport hooks, which are designed to collect system information during crash reporting processes. When these hooks execute the problematic read_file() function, they inadvertently create pathways for information disclosure that could compromise system integrity and confidentiality.
The technical implementation of this vulnerability stems from inadequate validation and handling of file types within the read_file() function. The function fails to properly check whether the target file is a symbolic link or named pipe before attempting to read its contents, directly violating security principles that require proper file access control and validation. According to CWE-22, this vulnerability aligns with improper limitation of a pathname to a restricted directory, as the function does not adequately restrict file access paths. The flaw essentially allows for arbitrary file access through symlink traversal, enabling attackers to bypass normal file permissions and access files they would otherwise not have access to. This behavior creates a privilege escalation vector that could be exploited by local users to gain unauthorized access to sensitive system data, configuration files, or user-specific information that should remain protected.
The operational impact of CVE-2021-32551 extends beyond simple information disclosure to encompass potential system compromise and data integrity violations. When the openjdk-15 package's apport hooks execute the vulnerable function during crash reporting, they may inadvertently expose private data such as passwords, cryptographic keys, or system configuration details stored in files accessible through symbolic links or named pipes. This vulnerability is particularly dangerous in multi-user environments where local users might attempt to create symbolic links pointing to sensitive system files or exploit FIFOs to gain unauthorized access to data. The attack surface is amplified because apport hooks are designed to collect comprehensive system information during application crashes, making them ideal targets for exploitation. This vulnerability directly maps to ATT&CK technique T1005, which involves data from local system, and T1059, which covers command and scripting interpreter usage for privilege escalation.
Mitigation strategies for CVE-2021-32551 should focus on implementing proper file access validation and restricting symbolic link traversal within the read_file() function. The most effective approach involves modifying the function to explicitly check file types and reject symbolic links or FIFOs during file operations, thereby preventing unauthorized access to sensitive data. System administrators should ensure that affected systems are updated with patches that address this vulnerability in the apport package, particularly those that implement proper file descriptor validation and access control mechanisms. Organizations should also consider implementing monitoring solutions that can detect suspicious file access patterns or attempts to create symbolic links in system directories where apport hooks operate. Additionally, the vulnerability highlights the importance of proper input validation and file access control in security-critical applications, aligning with security frameworks such as the OWASP Top 10 and NIST cybersecurity guidelines that emphasize the need for robust access control and privilege separation in system components that handle sensitive data. Regular security audits and penetration testing should be conducted to identify similar vulnerabilities in other system components that may exhibit similar behaviors.