CVE-2021-32550 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-14 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-2021-32550 resides within the apport package's hookutils.py module, specifically in the read_file() function implementation. This flaw represents a significant security weakness in Ubuntu's crash reporting system that could potentially lead to information disclosure. The issue manifests when the read_file() function processes symbolic links or opens named pipes, creating pathways for unauthorized data access. The vulnerability is particularly concerning because it affects the openjdk-14 package's apport hooks, which are designed to collect system information when java applications crash. When these hooks execute the problematic read_file() function, they inadvertently create opportunities for local users to access sensitive data that should remain protected. This vulnerability directly relates to CWE-22, which describes improper limitation of a pathname to a restricted directory, and CWE-352, which covers cross-site request forgery. The attack surface expands when considering that apport hooks are typically executed with elevated privileges during crash reporting, making the potential impact more severe than a simple path traversal attack.
The operational impact of this vulnerability extends beyond simple data exposure, as it enables local privilege escalation scenarios where malicious users can craft symbolic links or FIFOs that point to sensitive system files. When the openjdk-14 package's apport hooks process these malicious links, they can inadvertently read confidential information such as passwords, cryptographic keys, or other private data stored in system directories. The vulnerability's exploitation requires local access to the system, but the potential for data leakage makes it particularly dangerous in multi-user environments where different users share the same system resources. Attackers could create symbolic links pointing to sensitive files like /etc/shadow, /etc/passwd, or application-specific configuration files containing database credentials. The function's behavior becomes particularly problematic when dealing with FIFOs, as these named pipes can be used to create unexpected data flows that bypass normal file access controls. This vulnerability aligns with ATT&CK technique T1005, which covers data from local system, and T1059, which involves command and scripting interpreter usage. The exploitation chain typically involves creating malicious symbolic links or named pipes in directories accessible to the target user, then triggering the openjdk-14 apport hooks through java application crashes or system events that invoke the affected functionality.
Mitigation strategies for CVE-2021-32550 should focus on both immediate patching and defensive configuration measures. The primary solution involves updating the affected apport package to a version that properly handles symbolic links and FIFOs within the read_file() function, preventing the traversal of unauthorized file paths. System administrators should ensure that all systems running openjdk-14 packages are updated with the latest security patches from Ubuntu's repositories. Additionally, implementing strict file system permissions and access controls can help limit the damage from potential exploitation attempts. Organizations should consider disabling or restricting apport hooks that process sensitive data, particularly in environments where multiple users share system resources. The implementation of file integrity monitoring solutions can help detect suspicious symbolic link creation or FIFO manipulation attempts. Security teams should also review and audit existing apport hook configurations to ensure that no unnecessary access to sensitive system resources is granted. Network segmentation and privilege separation measures can further reduce the potential impact of exploitation. Regular security assessments should include verification that symbolic links and FIFOs are properly handled within system utilities, particularly those involved in crash reporting and system diagnostics. The vulnerability demonstrates the importance of secure coding practices in system utilities and highlights the need for comprehensive input validation and access control mechanisms in all file processing functions, especially those that operate with elevated privileges during system maintenance operations.