CVE-2007-2063 in SSH Server
Summary
by MITRE
SSH Tectia Server for IBM z/OS before 5.4.0 uses insecure world-writable permissions for (1) the server pid file, which allows local users to cause arbitrary processes to be stopped, or (2) when _BPX_BATCH_UMASK is missing from the environment, creates HFS files with insecure permissions, which allows local users to read or modify these files and have other unknown impact.
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Analysis
by VulDB Data Team • 07/27/2019
The vulnerability identified as CVE-2007-2063 affects SSH Tectia Server for IBM z/OS versions prior to 5.4.0, presenting significant security risks through improper file permission handling. This issue manifests in two distinct but related security flaws that collectively undermine the integrity and confidentiality of the system. The primary concern involves the server pid file being created with world-writable permissions, while the secondary issue occurs when the _BPX_BATCH_UMASK environment variable is absent, leading to insecure HFS file creation with overly permissive access controls.
The technical flaw stems from the server's failure to properly enforce access controls during file creation processes. When the server pid file is created with world-writable permissions, any local user can modify this critical file to contain arbitrary process identifiers, potentially allowing them to send termination signals to running processes or manipulate the server's operational state. This represents a direct violation of the principle of least privilege and creates opportunities for denial of service attacks or process injection. The second vulnerability occurs when _BPX_BATCH_UMASK is not properly set in the environment, causing HFS files to be created with default permissions that may include read or write access for all users, thereby exposing sensitive data and system components to unauthorized access.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it creates multiple attack vectors for local users who may not have direct administrative access. An attacker could potentially disrupt critical system services by manipulating the pid file, or gain unauthorized access to sensitive information stored in HFS files. The unknown impact mentioned in the description suggests that the insecure file permissions may enable additional attack surfaces that are not immediately apparent, potentially allowing for privilege escalation or data exfiltration. This vulnerability particularly affects systems where multiple users share the same system resources and where proper security hardening has not been implemented.
Security mitigations for this vulnerability require immediate implementation of proper file permission controls and environment variable management. System administrators should ensure that the _BPX_BATCH_UMASK environment variable is properly configured to enforce restrictive file permissions, typically setting it to 077 or similar restrictive values. The server pid file permissions should be explicitly set to restrictive access controls, ensuring that only the appropriate user or process can modify it. Additionally, regular security audits should verify that no world-writable files exist in critical system directories. This vulnerability aligns with CWE-732, which addresses inadequate permissions for critical resources, and represents a clear violation of the principle of least privilege. Organizations should also consider implementing automated monitoring solutions to detect and alert on insecure file permissions, as well as ensuring that all systems are updated to SSH Tectia Server 5.4.0 or later versions where these issues have been resolved. The ATT&CK framework would classify this vulnerability under privilege escalation techniques, specifically targeting local privilege escalation through insecure file permissions and process manipulation.