Executive brief
A vulnerability in the password management utility of Digital Unix 3.x allows local users to overwrite or create system files. This occurs because the utility handles log files insecurely, allowing a user to redirect log data to sensitive locations. An attacker could use this to disrupt system operations or potentially gain elevated administrative privileges.
Technical details
The dxchpwd utility, which is part of the C2 security package and typically installed setuid root, creates a log file at /tmp/dxchpwd.log. Because the application does not securely check for the existence of this file before writing to it, a local attacker can create a symbolic link from /tmp/dxchpwd.log to any target file on the system. When dxchpwd is executed, it follows the symlink and writes log data to the target path with root privileges. This can be used to overwrite critical system files or create new files owned by root, potentially leading to a denial of service or privilege escalation (e.g., by modifying .rhosts). A temporary fix involves manually creating /tmp/dxchpwd.log as a root-owned file with restricted permissions.
Affected products
- Digital Equipment Corporation Digital Unix (OSF/1) 3.x
Timeline
- 1996-11-17: disclosed: Vulnerability reported to Bugtraq mailing list.
- 1996-11-17: advisory