CVE-2013-2777 in sudo
Summary
by MITRE
sudo before 1.7.10p5 and 1.8.x before 1.8.6p6, 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 a session without a controlling terminal device and 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 • 01/02/2022
The vulnerability described in CVE-2013-2777 represents a critical privilege escalation flaw in the sudo command that affects versions prior to 1.7.10p5 and 1.8.6p6 when the tty_tickets option is enabled. This issue stems from insufficient validation of controlling terminal devices within the sudo authorization mechanism, creating a significant security weakness that can be exploited by local attackers with sudo permissions. The vulnerability specifically targets the session management component of sudo, where the system fails to properly verify terminal ownership and control, allowing malicious users to manipulate authorization contexts across different terminal sessions.
The technical flaw manifests when sudo operates with the tty_tickets option enabled, which is designed to associate authentication tokens with specific terminal sessions. However, the implementation contains a critical gap in terminal device validation that permits an attacker to establish a connection to the stdin, stdout, and stderr file descriptors of another terminal session. This misconfiguration enables the hijacking of authorization contexts, allowing an attacker to leverage another user's sudo credentials and execute commands with elevated privileges without proper authentication. The vulnerability exploits the fundamental assumption that terminal sessions maintain proper isolation and that controlling terminal devices are properly validated during authorization processes.
From an operational impact perspective, this vulnerability represents a severe threat to system security since it allows local users with existing sudo permissions to escalate their privileges without requiring additional authentication mechanisms. The attack vector specifically targets scenarios where multiple users share a system and utilize sudo for privilege escalation, creating a pathway for unauthorized privilege escalation that bypasses normal authentication checks. The vulnerability can be particularly dangerous in multi-user environments where administrators rely on sudo for access control, as it essentially allows any user with sudo access to potentially gain access to other users' administrative privileges.
The exploitation of this vulnerability aligns with several attack patterns documented in the MITRE ATT&CK framework, particularly those related to privilege escalation and credential access. This issue can be classified under CWE-284 Access Control Issues, where insufficient controls over terminal session management lead to unauthorized access to privileged resources. The vulnerability also demonstrates characteristics of CWE-352 Cross-Site Request Forgery in the context of local privilege escalation, where the system fails to properly validate session contexts. Organizations should consider implementing additional monitoring and access control measures to detect unusual terminal session behavior and unauthorized access attempts that could indicate exploitation of this vulnerability.
Mitigation strategies for CVE-2013-2777 primarily focus on updating sudo to versions that address the terminal validation flaw, specifically ensuring systems are running sudo 1.7.10p5 or later, or 1.8.6p6 or later. System administrators should also consider disabling the tty_tickets option in sudoers configuration files when it is not strictly required, as this removes the attack surface for this particular vulnerability. Additional protective measures include implementing strict terminal session management policies, monitoring for unauthorized terminal access patterns, and conducting regular security audits to identify and remediate similar privilege escalation vulnerabilities. Organizations should also review their sudoers configurations to ensure proper access controls and limit sudo permissions to only those users who require elevated privileges, reducing the overall risk exposure from this and related vulnerabilities.