CVE-2011-1709 in gdm
Summary
by MITRE
GNOME Display Manager (gdm) before 2.32.2, when glib 2.28 is used, enables execution of a web browser with the uid of the gdm account, which allows local users to gain privileges via vectors involving the x-scheme-handler/http MIME type.
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Analysis
by VulDB Data Team • 11/08/2021
The vulnerability identified as CVE-2011-1709 represents a critical privilege escalation flaw within the GNOME Display Manager (GDM) component that affected versions prior to 2.32.2. This issue specifically manifests when GDM operates in conjunction with glib 2.28, creating an exploitable condition that allows local attackers to elevate their system privileges through carefully crafted web browser execution scenarios. The vulnerability stems from improper handling of MIME type associations within the display manager's execution context, particularly concerning the x-scheme-handler/http MIME type which governs how HTTP URLs are processed by web browsers.
The technical exploitation mechanism involves the manipulation of the x-scheme-handler/http MIME type registration within the desktop environment's configuration. When GDM executes web browser applications, it does so under the context of the gdm account's user identifier rather than the invoking user's privileges. This creates a scenario where local users can manipulate the system's MIME type handling to execute arbitrary commands with elevated privileges. The vulnerability is categorized under CWE-284 Access Control, specifically related to improper privileges management during application execution contexts. Attackers can leverage this weakness by crafting malicious MIME type associations that, when processed through the GDM framework, result in execution of commands with the elevated gdm account privileges.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with a persistent method to gain administrative control over affected systems. Since GDM typically runs with elevated privileges to manage user sessions and display services, any compromise of this component can lead to complete system takeover. The attack vector specifically targets local users who can leverage the system's desktop environment configuration to execute malicious code. This vulnerability aligns with ATT&CK technique T1068 Privilege Escalation through the use of legitimate system tools and processes to gain elevated privileges, and represents a classic case of privilege escalation via service misconfiguration.
Mitigation strategies for CVE-2011-1709 require immediate patching of affected GDM installations to version 2.32.2 or later, which addresses the improper privilege handling during web browser execution. System administrators should also implement strict controls over MIME type associations within desktop environments, particularly restricting modifications to x-scheme-handler protocols. Additional protective measures include implementing proper access controls for desktop environment configuration files and monitoring for unauthorized changes to system-wide MIME type registrations. The vulnerability demonstrates the importance of privilege separation in display managers and the need for careful consideration of execution contexts when handling user-initiated applications within system services. Organizations should also consider implementing application whitelisting policies to prevent execution of untrusted applications through the display manager framework.