CVE-2013-2776 in sudo
Summary
by MITRE
sudo 1.3.5 through 1.7.10p5 and 1.8.0 through 1.8.6p6, when running on systems without /proc or the sysctl function with the tty_tickets option 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 • 01/02/2022
The vulnerability identified as CVE-2013-2776 represents a critical authorization bypass flaw in the sudo command execution mechanism on Unix-like systems. This security issue affects sudo versions ranging from 1.3.5 through 1.7.10p5 and 1.8.0 through 1.8.6p6, specifically when operating on systems lacking /proc filesystem access or systems where the sysctl function with tty_tickets option is disabled. The flaw stems from insufficient validation of controlling terminal devices during sudo execution, creating a pathway for malicious users to exploit terminal session hijacking techniques. The vulnerability operates under the broader context of privilege escalation attacks where local users with existing sudo permissions can manipulate the authorization context of other terminal sessions.
The technical implementation of this vulnerability exploits the improper handling of file descriptor connections between terminal sessions. When sudo operates without proper terminal device validation, it fails to verify that the controlling terminal matches the expected session context. This weakness allows an attacker to connect to the standard input, output, and error file descriptors of another terminal session, effectively hijacking the authorization context. The flaw specifically manifests when sudo attempts to establish terminal control without sufficient validation of the terminal device identity, creating a window where malicious input can be redirected to legitimate user sessions. This type of vulnerability falls under the CWE-284 access control weakness category, specifically related to improper privileges and insufficient validation of terminal contexts.
The operational impact of CVE-2013-2776 extends beyond simple privilege escalation to encompass broader session hijacking capabilities that can compromise system integrity and user confidentiality. Local users with sudo permissions can leverage this vulnerability to execute commands in the context of other terminal sessions, potentially accessing sensitive data or performing unauthorized administrative actions. The attack vector is particularly dangerous because it requires minimal privileges to initiate and can be executed without requiring additional system compromise. This vulnerability affects systems where the tty_tickets option is enabled, creating a scenario where sudo's terminal validation mechanisms are bypassed, allowing attackers to manipulate session contexts through file descriptor redirection. The implications align with ATT&CK technique T1068 for local privilege escalation and T1548 for abuse of sudo privileges.
Mitigation strategies for CVE-2013-2776 require immediate system updates to patched sudo versions that properly validate terminal device contexts. Organizations should ensure their sudo installations are updated to versions that address the specific terminal validation flaws present in the affected ranges. System administrators should also consider disabling the tty_tickets option if it is not essential for their operational requirements, as this reduces the attack surface for this specific vulnerability. Additionally, implementing comprehensive monitoring of sudo usage patterns can help detect anomalous terminal session behaviors that might indicate exploitation attempts. Security configurations should enforce strict terminal device validation policies and ensure that all sudo operations properly verify controlling terminal identities before proceeding with authorization checks. The vulnerability highlights the importance of maintaining updated system components and proper privilege management policies to prevent unauthorized session manipulation and maintain system security integrity.