CVE-2016-9951 in Apport
Summary
by MITRE
An issue was discovered in Apport before 2.20.4. A malicious Apport crash file can contain a restart command in `RespawnCommand` or `ProcCmdline` fields. This command will be executed if a user clicks the Relaunch button on the Apport prompt from the malicious crash file. The fix is to only show the Relaunch button on Apport crash files generated by local systems. The Relaunch button will be hidden when crash files are opened directly in Apport-GTK.
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Analysis
by VulDB Data Team • 10/27/2024
The vulnerability identified as CVE-2016-9951 resides within the Apport crash reporting system, a critical component of Ubuntu and Debian-based Linux distributions designed to collect and report system crash information. This security flaw represents a sophisticated privilege escalation vector that exploits the trust model inherent in desktop crash reporting mechanisms. The vulnerability specifically affects Apport versions prior to 2.20.4, where the system fails to properly validate the origin of crash reports, creating an opportunity for malicious actors to craft specially crafted crash files that can execute arbitrary commands on target systems. The flaw operates through a carefully constructed deception mechanism that leverages the user-facing graphical interface of Apport-GTK, which displays crash information and provides interactive options to users.
The technical implementation of this vulnerability exploits the trust relationship between the Apport crash reporting system and end users by manipulating specific fields within crash report files. Malicious actors can craft crash files containing crafted `RespawnCommand` or `ProcCmdline` fields that contain executable commands. When users interact with these malicious crash reports through the Apport-GTK interface, clicking the Relaunch button triggers the execution of these commands with the privileges of the user who clicked the button. This represents a classic social engineering attack combined with a software vulnerability, where the user's interaction becomes the execution vector for malicious code. The vulnerability specifically targets the graphical user interface component of Apport, making it particularly dangerous as it requires no specialized technical knowledge from the attacker beyond the ability to create malicious crash files.
The operational impact of CVE-2016-9951 extends beyond simple command execution to encompass potential privilege escalation and system compromise scenarios. When executed successfully, these malicious commands can perform actions ranging from simple file manipulation to more sophisticated attacks including privilege escalation, data exfiltration, or system reconnaissance. The vulnerability is particularly concerning in environments where users may encounter crash reports from untrusted sources or where automated crash reporting systems might process external crash files. The attack vector is inherently user-dependent, requiring the target to actively interact with the malicious crash file through the Apport-GTK interface, but this dependency also makes the vulnerability particularly stealthy as legitimate crash reports may appear to be from trusted sources. The security implications align with CWE-78, which addresses improper neutralization of special elements used in OS commands, and the attack pattern maps to T1059, the execution of system commands through legitimate interfaces.
The remediation strategy for CVE-2016-9951 implements a fundamental security principle of least privilege and origin verification through the introduction of a validation mechanism that restricts the availability of the Relaunch button. The fix specifically ensures that the Relaunch functionality is only enabled for crash files generated by local systems, effectively blocking the execution of malicious commands from externally sourced crash reports. This approach addresses the core issue by breaking the trust model that enabled the attack, preventing the execution of arbitrary commands from untrusted sources. The solution demonstrates the importance of input validation and origin verification in security-critical systems, as it prevents the escalation of privilege through user interaction with potentially malicious content. This fix aligns with defensive programming practices that emphasize validating all inputs and restricting functionality based on trust levels, thereby preventing the exploitation of trust-based security models that are common in desktop environments. The implementation effectively neutralizes the vulnerability by ensuring that the Relaunch button remains hidden when crash files are opened directly in Apport-GTK, preventing any possibility of command execution from malicious sources.