CVE-2009-1573 in xvfb-run
Summary
by MITRE
xvfb-run 1.6.1 in Debian GNU/Linux, Ubuntu, Fedora 10, and possibly other operating systems place the magic cookie (MCOOKIE) on the command line, which allows local users to gain privileges by listing the process and its arguments.
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Analysis
by VulDB Data Team • 08/11/2021
The vulnerability described in CVE-2009-1573 affects the xvfb-run utility version 1.6.1 across multiple Linux distributions including Debian, Ubuntu, and Fedora 10. This utility is designed to run X11 applications in a virtual framebuffer environment, commonly used for automated testing and headless operations. The core issue lies in how the utility handles authentication cookies during its execution process, specifically placing the magic cookie value directly on the command line arguments. This design flaw creates a significant security exposure that can be exploited by local users with minimal privileges.
The technical implementation of this vulnerability stems from the fact that when xvfb-run starts a virtual X server, it generates an authentication cookie that serves as the primary means of securing access to the X11 display. In the affected versions, this authentication cookie is passed as a command line argument to the underlying X server process rather than being handled through secure file-based mechanisms or environment variables. The command line arguments of running processes are accessible to all users on the system through standard process enumeration tools such as ps, which means that any local user can easily retrieve the authentication cookie by simply listing running processes and examining their arguments. This violates fundamental security principles of least privilege and secure credential handling.
The operational impact of this vulnerability is substantial as it allows any local user to escalate their privileges and gain unauthorized access to the X11 display server. An attacker can leverage this information to perform actions such as capturing screenshots, controlling the display, or executing unauthorized graphical operations. The vulnerability represents a classic case of insecure credential storage and exposure, where sensitive authentication information is stored in an easily accessible location. This type of flaw falls under the CWE category of CWE-255 Credentials Management, specifically addressing the improper handling of authentication tokens and the exposure of sensitive information through insecure command line argument passing.
The security implications extend beyond simple privilege escalation as this vulnerability can be exploited in conjunction with other attack vectors to create more sophisticated attacks. For instance, an attacker could use the gained access to X11 functionality to capture user credentials from graphical applications or perform screen scraping operations. The vulnerability also demonstrates poor adherence to the principle of least privilege, as the authentication cookie should never be exposed through command line arguments given the potential for privilege escalation. This flaw aligns with ATT&CK technique T1068, which covers privilege escalation through the exploitation of insecure credential handling mechanisms, and T1548.003, which addresses abuse of command-line arguments for privilege escalation purposes.
Mitigation strategies for this vulnerability include upgrading to patched versions of xvfb-run where the authentication cookie is no longer exposed on the command line, typically through the implementation of secure file-based credential handling or environment variable passing. System administrators should also implement monitoring for unusual process execution patterns and ensure that command line arguments containing sensitive information are not exposed to unauthorized users. Additional protective measures include restricting access to processes that may expose sensitive information and implementing proper process isolation techniques. The vulnerability highlights the importance of secure coding practices and the need for thorough security reviews of command line argument handling in system utilities, particularly those that deal with authentication mechanisms and privileged operations.