apcupsd Unsafe File Permissions Let Local Users Kill Arbitrary Processes
SecurityTracker Alert ID: 1008774|
SecurityTracker URL: http://securitytracker.com/id/1008774
(Links to External Site)
Date: Jan 20 2004
Denial of service via local system|
Fix Available: Yes Vendor Confirmed: Yes Exploit Included: Yes |
Version(s): 3.7.2 and possibly earlier versions|
A denial of service vulnerability was reported in apcupsd. A local user can cause arbitrary processes on the target system to be killed.|
In December 2000, it was reported that the software creates a temporary file ('apcupsd.pid') in the /var/run directory and assigns unsafe 0666 permissions (i.e., global read and write permissions) to the file. A local user can overwrite the contents of the file with arbitrary process IDs to cause the specified processes to be killed by apcupsd when the daemon is restarted or stopped or when the the daemon performs shutdown.
The vendor was reported notified on July 12, 2000.
A local user can cause arbitrary processes on the target system to be killed.|
The vendor has released a fixed version (3.8.0), available at:|
Vendor URL: www.apcupsd.com/ (Links to External Site)
Access control error, Configuration error|
|Underlying OS: Linux (Any), UNIX (Any)|
Source Message Contents
Subject: apcupsd 3.7.2 Denial of Service|
Title: apcupsd 3.7.2 Denial of Service
Affected Application: apcupsd daemon
Affected Versions: 3.7.2 and maybe prior
Not affected: 3.8.0 and above
Affected Platforms: all Linux / Unix
Vulnerability Class: Denial of Service (local)
Author Notified: Yes July 12th 2000
Fix available: Yes (included)
Apcupsd is a daemon for controlling most of APC's UPS models on Unix and
Windows machines. The Unix daemon runs as root and shuts the machine down in
case of a power failure.
During startup apcupsd creates a PID-file named "apcupsd.pid" in /var/run
(system specific, maybe other directory) with the ID of the daemon process,
this PID-file is used by the shutdown-script to kill the daemon process.
Unfortunatly this PID-file ist world-writeable (Mode 666, -rw-rw-rw). A
malicious user can overwrite the file with arbitrary process ID's, these
processes will be killed instead of the apcupsd process during restart or
stop of the apcupsd daemon and during system shutdown or restart, the whole
system can be crashed this way.
Upgrade to apcupsd Version 3.8.0 .
It's available at:
User's who don't want to upgrade can add two lines to the "start" section in
the apcupsd startup script in /etc/rc.d or /sbin/init.d :
rm -f /etc/apcupsd/powerfail
rm -f /etc/nologin
echo -n "Starting apcupsd power management"
$APCUPSD || return=$rc_failed
# give the daemon some little time to create the PID-file
#now simply chmod the PID-file to Mode 644
chmod 644 /var/run/apcupsd.pid
echo -e "$return"