CVE-2013-1776 in sudo
Summary
by MITRE
sudo 1.3.5 through 1.7.10 and 1.8.0 through 1.8.5, when the tty_tickets option is enabled, does not properly validate the controlling terminal device, which allows local users with sudo permissions to hijack the authorization of another terminal via vectors related to connecting to the standard input, output, and error file descriptors of another terminal. NOTE: this is one of three closely-related vulnerabilities that were originally assigned CVE-2013-1776, but they have been SPLIT because of different affected versions.
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Analysis
by VulDB Data Team • 05/05/2021
The vulnerability identified as CVE-2013-1776 represents a critical security flaw in the sudo command that affects versions ranging from 1.3.5 through 1.7.10 and 1.8.0 through 1.8.5. This issue specifically manifests when the tty_tickets option is enabled, creating a scenario where local users with sudo privileges can exploit a weakness in terminal device validation. The vulnerability stems from the improper validation of controlling terminal devices, which creates an avenue for privilege escalation and unauthorized access to system resources. This flaw operates at the core of Unix-like operating systems' privilege management mechanisms, where sudo serves as the primary interface for authorized users to execute commands with elevated privileges.
The technical implementation of this vulnerability involves a race condition and improper file descriptor handling within the sudo command's terminal management system. When tty_tickets is enabled, sudo maintains authentication tickets associated with specific terminal sessions. However, the validation process fails to properly verify the controlling terminal device, allowing malicious users to manipulate file descriptors connected to standard input, output, and error streams of other terminal sessions. This manipulation enables attackers to hijack authentication tickets and gain unauthorized access to resources that should be restricted to legitimate users. The vulnerability operates through the exploitation of the relationship between process file descriptors and terminal devices, where the system fails to validate that the current terminal session matches the expected controlling terminal for the authentication ticket.
The operational impact of this vulnerability extends beyond simple privilege escalation, creating potential for broader system compromise and unauthorized access to sensitive resources. An attacker with sudo permissions can effectively impersonate other users within the same terminal session, potentially accessing confidential data, executing unauthorized commands, or maintaining persistent access to system resources. This vulnerability particularly affects multi-user environments where multiple individuals share the same system and sudo access is granted to various users. The implications become more severe in enterprise environments where sudo is commonly used for administrative tasks, as it could enable attackers to bypass security controls and escalate privileges to gain access to critical system components and data repositories.
Security professionals should consider this vulnerability in the context of the CWE-284 access control weakness classification, which specifically addresses improper access control mechanisms in software systems. The vulnerability also aligns with ATT&CK technique T1068, which describes the use of local privilege escalation techniques through exploitation of system vulnerabilities. Organizations should implement immediate mitigations including updating sudo to versions that address this vulnerability, disabling the tty_tickets option when not required, and monitoring for suspicious terminal session activity. Additionally, system administrators should conduct thorough audits of sudo configurations and user permissions to ensure that only necessary users have sudo access, thereby reducing the attack surface for this and similar vulnerabilities. The remediation process should include comprehensive testing to ensure that updated configurations maintain system functionality while eliminating the security risk.