CVE-2021-32553 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-17 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-2021-32553 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-17 package's apport hooks for crash reporting and system diagnostics. The vulnerability stems from insufficient validation of file system objects when processing file reads, creating an avenue for unauthorized data exposure. Apport serves as Ubuntu's crash reporting system, collecting system information when applications fail, and its integration with openjdk-17 means that Java-related crash reports may inadvertently trigger this vulnerability during data collection processes.
The technical flaw manifests when the read_file() function processes symbolic links or FIFO (named pipe) objects without proper safeguards against their traversal or opening. This behavior violates fundamental security principles by allowing arbitrary file access patterns that could be exploited by malicious local users. When the openjdk-17 package's apport hooks invoke this function, the system's file access controls become bypassed, enabling potential data leakage from sensitive system locations. The vulnerability operates at the file system abstraction layer, where symbolic link resolution and FIFO handling are not properly constrained, creating a path for information disclosure attacks. This issue aligns with CWE-22, which addresses improper limitation of a pathname to a restricted directory, and CWE-377, which covers insecure temporary file creation.
The operational impact of CVE-2021-32553 extends beyond simple data exposure, as it creates persistent security risks for systems running affected software configurations. Local users who can manipulate symbolic links or create FIFOs in accessible directories can leverage this vulnerability to access private data that should remain protected. The exposure could include sensitive configuration files, system logs, user credentials, or application-specific data that may be collected by apport during crash reporting. This vulnerability particularly affects systems where multiple users share the same environment, as it enables privilege escalation through information gathering and potential exploitation of other system weaknesses. The attack vector operates through legitimate system functionality, making detection more challenging as the behavior appears normal during crash reporting operations.
Mitigation strategies for this vulnerability require immediate patching of affected systems through updated package versions that properly validate file system objects before processing. System administrators should implement restrictive file permissions and monitor symbolic link creation in directories where apport hooks operate. The recommended approach includes disabling or restricting the use of symbolic links and FIFOs within the scope of apport's file processing functions. Organizations should also consider implementing additional logging and monitoring for suspicious file access patterns, particularly around crash reporting activities. Security controls should focus on privilege separation and limiting the scope of file system access within apport hooks to prevent unauthorized data exposure. This vulnerability demonstrates the importance of proper input validation and secure file handling practices in system-level components, aligning with ATT&CK technique T1059.007 for execution through scripting and T1566.001 for credential access through privilege escalation.