CVE-2018-6552 in Apport
Summary
by MITRE
Apport does not properly handle crashes originating from a PID namespace allowing local users to create certain files as root which an attacker could leverage to perform a denial of service via resource exhaustion, possibly gain root privileges, or escape from containers. The is_same_ns() function returns True when /proc/<global pid>/ does not exist in order to indicate that the crash should be handled in the global namespace rather than inside of a container. However, the portion of the data/apport code that decides whether or not to forward a crash to a container does not always replace sys.argv[1] with the value stored in the host_pid variable when /proc/<global pid>/ does not exist which results in the container pid being used in the global namespace. This flaw affects versions 2.20.8-0ubuntu4 through 2.20.9-0ubuntu7, 2.20.7-0ubuntu3.7, 2.20.7-0ubuntu3.8, and 2.20.1-0ubuntu2.15 through 2.20.1-0ubuntu2.17.
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Analysis
by VulDB Data Team • 03/19/2023
The vulnerability described in CVE-2018-6552 resides within the apport crash handling mechanism of ubuntu systems, specifically targeting the improper management of crashes originating from PID namespace contexts. This flaw represents a critical security issue that undermines the isolation properties of containerized environments while potentially enabling privilege escalation and denial of service attacks. The vulnerability stems from a fundamental mismanagement of process identification and namespace handling within the apport subsystem, which is responsible for collecting crash information and generating diagnostic reports for applications that have failed.
The technical root cause lies in the is_same_ns() function's behavior when encountering non-existent process entries in the /proc filesystem. When /proc/<global pid>/ directory structure cannot be found, this function incorrectly returns True to indicate that the crash should be handled in the global namespace rather than within a container context. However, the subsequent code path responsible for determining whether to forward crash information to containerized processes fails to consistently replace sys.argv[1] with the host_pid value when the global process directory is missing. This inconsistency creates a scenario where containerized processes continue to use their container-specific PIDs even when operating in the global namespace context, leading to improper file creation permissions and namespace handling.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to encompass potential privilege escalation and container escape capabilities. Local attackers can exploit this flaw to create arbitrary files as the root user within the global namespace, effectively bypassing the security boundaries that containerization is designed to enforce. This capability enables attackers to manipulate system resources, potentially leading to resource exhaustion attacks that can bring down critical services or systems. The vulnerability particularly affects Ubuntu systems running specific versions of apport, including releases from 2.20.8-0ubuntu4 through 2.20.9-0ubuntu7 and various point releases in the 2.20.7 and 2.20.1 series, making it a widespread concern across multiple Ubuntu LTS and standard releases.
From a cybersecurity perspective, this vulnerability aligns with CWE-284 (Improper Access Control) and CWE-269 (Improper Privilege Management) categories, representing a failure in proper privilege handling and namespace isolation. The attack vector maps to ATT&CK technique T1068 (Exploitation for Privilege Escalation) and T1059 (Command and Scripting Interpreter) as attackers could leverage the privilege escalation to execute malicious code. The vulnerability also demonstrates characteristics of container escape techniques, making it particularly dangerous in environments where containerization is extensively used for application deployment and isolation. Organizations should prioritize patching affected systems and implementing additional monitoring for unauthorized file creation in system directories, especially those with elevated permissions. The flaw underscores the critical importance of proper namespace handling in security-sensitive components and highlights the potential for seemingly minor code path issues to create significant security vulnerabilities in containerized environments.