CVE-2019-11481 in Apport
Summary
by MITRE
Kevin Backhouse discovered that apport would read a user-supplied configuration file with elevated privileges. By replacing the file with a symbolic link, a user could get apport to read any file on the system as root, with unknown consequences.
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Analysis
by VulDB Data Team • 06/18/2024
The vulnerability identified as CVE-2019-11481 resides within the apport package, a crash reporting utility commonly found in ubuntu and debian based systems. This flaw represents a classic privilege escalation vulnerability that exploits the improper handling of configuration files during system crash reporting processes. The apport utility is designed to collect system information when applications crash, but it inadvertently creates a security risk by executing user-supplied configuration files with root privileges. The vulnerability specifically manifests when apport processes a configuration file that has been replaced with a symbolic link, allowing an attacker to manipulate the file reading process to access arbitrary system files. This issue directly violates the principle of least privilege and demonstrates a critical flaw in access control mechanisms within system utilities.
The technical implementation of this vulnerability stems from apport's failure to properly validate file paths when processing configuration files. When a symbolic link is present in the expected configuration file location, the utility follows the link and reads the target file with elevated privileges. This behavior creates a race condition and path traversal scenario where an unprivileged user can manipulate the file system to redirect apport's file reading operations to sensitive system files such as /etc/shadow, /etc/passwd, or other critical configuration resources. The vulnerability is particularly dangerous because it operates within the system's privilege escalation framework, allowing an attacker to execute arbitrary file reads with root privileges. This flaw can be categorized under CWE-22 Path Traversal and CWE-73 Path Traversal, both of which relate to improper handling of file paths and symbolic links in system utilities.
The operational impact of CVE-2019-11481 extends beyond simple information disclosure to encompass potential complete system compromise. An attacker who successfully exploits this vulnerability can gain access to sensitive system files that contain authentication credentials, system configurations, and other critical data. The consequences are particularly severe because apport typically runs with elevated privileges, making it an attractive target for attackers seeking to escalate their privileges on affected systems. This vulnerability can be leveraged as part of a broader attack chain, potentially enabling further exploitation through privilege escalation to root access, or providing sensitive information that can be used for lateral movement within a network. The attack vector is relatively simple to execute, requiring only the ability to create symbolic links in specific locations, which makes it particularly concerning for systems where users have limited privileges but can still manipulate file system structures.
Mitigation strategies for CVE-2019-11481 should focus on both immediate patching and operational security improvements. The primary solution involves updating the apport package to a version that properly validates file paths and prevents symbolic link following during configuration file processing. System administrators should implement strict file system permissions and ensure that configuration directories are not writable by unprivileged users. Additionally, monitoring for unexpected symbolic link creation in system directories can help detect exploitation attempts. From an operational security perspective, implementing the principle of least privilege is crucial, ensuring that system utilities like apport do not run with unnecessary elevated privileges. The vulnerability also highlights the importance of proper input validation and file path handling in system utilities, which aligns with ATT&CK technique T1068 Privilege Escalation through exploitation of system vulnerabilities. Organizations should also consider implementing file integrity monitoring solutions to detect unauthorized changes to critical system files and directories that could be used in similar privilege escalation attacks.