CVE-2012-0943 in lightdm
Summary
by MITRE
debian/guest-account in Light Display Manager (lightdm) 1.0.x before 1.0.6 and 1.1.x before 1.1.7, as used in Ubuntu Linux 11.10, allows local users to delete arbitrary files via a space in the name of a file in /tmp. NOTE: this identifier was SPLIT per ADT1/ADT2 due to different codebases and affected versions. CVE-2012-6648 has been assigned for the gdm-guest-session issue.
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Analysis
by VulDB Data Team • 10/17/2024
The vulnerability identified as CVE-2012-0943 affects the Light Display Manager (lightdm) version 1.0.x before 1.0.6 and 1.1.x before 1.1.7, which was utilized in Ubuntu Linux 11.10. This security flaw represents a significant local privilege escalation vector that exploits improper handling of file names containing spaces within the /tmp directory. The vulnerability specifically targets the guest account functionality of lightdm, which is designed to provide temporary access to systems without requiring user authentication. The issue stems from a command injection vulnerability that occurs when the system processes file names with embedded spaces, creating a dangerous parsing scenario that can be exploited by local attackers to execute arbitrary commands with elevated privileges.
The technical flaw manifests in the way lightdm handles file names during guest session operations, particularly when processing files located in the /tmp directory. When a file with a space in its name is present in /tmp, the vulnerable code path fails to properly sanitize or escape the filename before executing system commands. This creates a classic shell injection vulnerability where attacker-controlled input can be interpreted as command-line arguments, allowing an attacker to manipulate the execution flow of system utilities. The vulnerability operates at the command-line parsing level where simple string manipulation fails to account for shell metacharacters, particularly spaces that separate command arguments. This flaw aligns with CWE-78, which describes improper neutralization of special elements used in OS commands, and represents a critical weakness in input validation and command construction practices.
The operational impact of this vulnerability is severe as it provides local users with the ability to delete arbitrary files on the system, potentially leading to complete system compromise. Attackers can leverage this vulnerability to remove critical system files, modify configuration data, or even escalate privileges to gain root access. The attack vector is particularly dangerous because it requires only local access to the system, making it difficult to detect in environments where local privilege escalation is not typically monitored. The vulnerability affects the guest account functionality specifically, which is often enabled in multi-user systems and may be accessible to untrusted users. This creates a persistent security risk where any user with access to the local system can exploit this flaw to cause significant damage to the system's integrity and availability. The issue is further compounded by the fact that the vulnerability was present in widely deployed versions of Ubuntu Linux, making it a significant concern for system administrators managing multiple affected systems.
Mitigation strategies for CVE-2012-0943 include immediate patching of affected lightdm versions to 1.0.6 or 1.1.7 respectively, which contain proper input sanitization and escape sequence handling. System administrators should also implement strict file naming conventions and avoid placing user-controlled files in the /tmp directory where possible. Additional protective measures include monitoring for unusual file deletion patterns in the /tmp directory and implementing proper file access controls to limit guest account privileges. The vulnerability demonstrates the importance of proper input validation and command construction in GUI display managers, as highlighted by ATT&CK technique T1059.001 for command and scripting interpreter. Organizations should also consider implementing automated patch management systems to ensure timely remediation of such vulnerabilities and establish monitoring protocols that can detect exploitation attempts through anomalous file system activity patterns.