CVE-2021-44513 in tmate-ssh-server
Summary
by MITRE • 12/07/2021
Insecure creation of temporary directories in tmate-ssh-server 2.3.0 allows a local attacker to compromise the integrity of session handling.
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Analysis
by VulDB Data Team • 10/03/2022
The vulnerability identified as CVE-2021-44513 affects tmate-ssh-server version 2.3.0 and represents a critical security flaw in the application's temporary directory handling mechanism. This issue stems from the insecure creation of temporary directories during session management operations, creating a significant attack surface for local adversaries seeking to compromise system integrity. The flaw specifically manifests when the application creates temporary files or directories without proper security controls, potentially allowing malicious users to manipulate these locations and gain unauthorized access to session data or system resources.
The technical root cause of this vulnerability lies in the improper implementation of temporary file and directory creation procedures within the tmate-ssh-server application. When the system generates temporary directories for session handling, it fails to establish appropriate security permissions or validate the directory creation process adequately. This insecure approach creates opportunities for race conditions or directory traversal attacks where an attacker can predict or manipulate temporary directory paths. The vulnerability aligns with CWE-377, which addresses insecure temporary file creation practices, and specifically relates to CWE-378, concerning the creation of temporary files with insecure permissions. The flaw essentially allows a local attacker to establish symbolic links or manipulate temporary directory structures before the legitimate application creates them, potentially leading to privilege escalation or session hijacking.
The operational impact of this vulnerability extends beyond simple local privilege escalation, as it directly compromises the integrity of session handling mechanisms within the tmate-ssh-server environment. Attackers can exploit this weakness to intercept or manipulate SSH session data, potentially gaining access to sensitive information or establishing persistent access to systems. The vulnerability particularly affects environments where tmate-ssh-server is used for remote access management or collaborative development sessions, where session integrity is paramount. From an attack perspective, this flaw maps to ATT&CK technique T1059.001 for command and script injection, and T1548.001 for abuse of privileges, as attackers can leverage the compromised temporary directories to execute malicious code or escalate their privileges within the system.
Mitigation strategies for CVE-2021-44513 should prioritize immediate patching of the tmate-ssh-server application to the latest version that addresses the insecure temporary directory creation issue. Organizations should implement proper temporary directory permissions and ensure that all temporary files are created with restrictive access controls, typically using umask settings or explicit permission specifications. The system should enforce secure temporary directory creation practices by utilizing established secure temporary file creation APIs or libraries that automatically handle proper permissions and path validation. Additionally, security monitoring should be enhanced to detect suspicious temporary directory creation patterns or unauthorized access attempts to session-related temporary files. System administrators should also consider implementing mandatory access controls or file system integrity monitoring to prevent unauthorized manipulation of temporary directories and maintain the integrity of session handling operations.