CVE-2021-32548 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-8 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-2021-32548 resides within the apport package's hookutils.py module, specifically in the read_file() function implementation. This flaw represents a critical security issue that affects systems utilizing the openjdk-8 package's apport hooks for crash reporting and system diagnostics. The vulnerability stems from insufficient validation of file system objects when processing file operations, creating an avenue for unauthorized data exposure. The apport framework serves as Ubuntu's default crash reporting system, collecting system information when applications crash, making this vulnerability particularly concerning for systems running Java applications that rely on apport for error reporting.
The technical flaw manifests through improper handling of symbolic links and named pipes during file reading operations. When the read_file() function encounters a symbolic link, it follows the link to the target file without validating whether the target is accessible or appropriate for the current context. Similarly, when processing FIFOs or named pipes, the function opens these special file types without adequate safeguards. This behavior allows local users to craft malicious symbolic link structures or named pipe configurations that can be exploited to access files otherwise protected by the system's file permissions. The vulnerability operates at the operating system level where file system access controls are bypassed through the flawed function implementation.
The operational impact of this vulnerability extends beyond simple data exposure, creating potential for privilege escalation and information disclosure attacks. When the openjdk-8 package's apport hooks invoke the vulnerable read_file() function, any local user can potentially access sensitive data that should normally be restricted to specific users or groups. This includes configuration files, log data, or other system information that may contain credentials, system details, or other confidential material. The vulnerability is particularly dangerous in multi-user environments where different users have varying levels of system access, as it allows lower-privileged users to potentially access data belonging to other users or system processes. The attack vector requires local system access but can be leveraged to extract valuable information from the system's file structure.
Mitigation strategies for CVE-2021-32548 should focus on immediate patching of affected systems, with the primary solution being the application of security updates provided by Ubuntu or the relevant distribution maintainers. System administrators should also implement additional security controls including restricting access to symbolic links within sensitive directories, implementing proper file system permissions, and monitoring for unauthorized symbolic link creation. The vulnerability aligns with CWE-59, which describes improper link resolution without limit, and can be mapped to ATT&CK technique T1083 for file and directory discovery. Organizations should also consider implementing file integrity monitoring solutions to detect unauthorized symbolic link creation and ensure that apport hooks are properly configured to avoid unnecessary file access operations. Regular security audits of system configuration files and access controls should be conducted to identify and remediate similar vulnerabilities across the system infrastructure.