CVE-2015-1338 in Apport
Summary
by MITRE
kernel_crashdump in Apport before 2.19 allows local users to cause a denial of service (disk consumption) or possibly gain privileges via a (1) symlink or (2) hard link attack on /var/crash/vmcore.log.
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Analysis
by VulDB Data Team • 11/24/2024
The vulnerability identified as CVE-2015-1338 resides within the kernel_crashdump functionality of Apport, a crash reporting tool used in Ubuntu and other Debian-based systems. This issue affects versions of Apport prior to 2.19 and represents a significant security concern due to its potential for both denial of service and privilege escalation. The flaw manifests when the system processes crash dump files, specifically targeting the /var/crash/vmcore.log file location where crash information is stored. This vulnerability operates under the broader category of improper access control and file system manipulation issues, which are categorized under CWE-284 in the Common Weakness Enumeration framework.
The technical exploitation of this vulnerability involves creating either symbolic links or hard links that point to critical system files or directories, thereby manipulating how the crash reporting system handles crash dump data. When kernel_crashdump processes these maliciously crafted links, it follows the symbolic or hard link references and writes crash information to unintended locations. This behavior can lead to disk space exhaustion when the system continuously writes to large files or directories, effectively causing a denial of service condition. The privilege escalation aspect occurs when the malicious link points to files that are writable by the crash reporting process but not by regular users, potentially allowing local attackers to modify system-critical files with elevated permissions.
The operational impact of this vulnerability extends beyond simple system availability issues as it provides attackers with a mechanism to consume system resources indefinitely while potentially gaining unauthorized access to system files. The /var/crash directory is typically managed with specific permissions to ensure only authorized processes can write to it, but the symlink and hard link attack bypasses these protections by leveraging the legitimate crash reporting functionality. Attackers can create a symlink pointing to a large file or directory, causing the system to continuously write data to that location until the disk is exhausted, or they can create a hard link to a system file that the crash reporting process can modify, potentially allowing privilege escalation.
Mitigation strategies for CVE-2015-1338 require immediate system updates to Apport version 2.19 or later, which includes patches addressing the symlink and hard link handling within the kernel_crashdump functionality. System administrators should also implement proper file system permissions and monitoring for the /var/crash directory, ensuring that only authorized processes can create or modify files within this critical location. Additionally, implementing proper file system integrity monitoring can help detect unauthorized symbolic or hard link creation attempts. The vulnerability demonstrates the importance of proper input validation and file system access controls, aligning with ATT&CK technique T1068 which covers privilege escalation through local exploits. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates and maintain comprehensive system monitoring to detect potential exploitation attempts.