Splunk version 6.6.x suffers from a local privilege escalation vulnerability. Splunk can be configured to run as a non-root user. However, that user owns the configuration file that specifies the user to run as, so it can trivially gain root privileges.
3e674b7b7b2bbcdc76d6019cc12711aaKL-001-2017-022 : Splunk Local Privilege Escalation
Title: Splunk Local Privilege Escalation
Advisory ID: KL-001-2017-022
Publication Date: 2017.11.03
Publication URL: https://www.korelogic.com/Resources/Advisories/KL-001-2017-022.txt
1. Vulnerability Details
Affected Vendor: Splunk
Affected Product: Splunk Enterprise
Affected Version: 6.6.x
Platform: Embedded Linux
CWE Classification: CWE-280: Improper Handling of Insufficient
Permissions or Privileges
Impact: Privilege Escalation
Attack vector: Local
2. Vulnerability Description
Splunk can be configured to run as a non-root user. However,
that user owns the configuration file that specifies the user
to run as, so it can trivially gain root privileges.
3. Technical Description
Splunk runs multiple daemons and network listeners as root
by default. It can be configured to drop privileges to a
specified non-root user at startup such as user splunk, via
the SPLUNK_OS_USER variable in the splunk-launch.conf file in
$SPLUNK_HOME/etc/ (such as /opt/splunk/etc/splunk-launch.conf).
However, the instructions for enabling such a setup call
for chown'ing the entire $SPLUNK_HOME directory to that same
non-root user. For instance:
http://docs.splunk.com/Documentation/Splunk/6.6.2/Installation/RunSplunkasadifferentornon-rootuser
"4. Run the chown command to change the ownership of the splunk
directory and everything under it to the user that you want
to run the software.
chown -R splunk:splunk $SPLUNK_HOME"
Therefore, if an attacker gains control of the splunk account,
they can modify $SPLUNK_HOME/etc/splunk-launch.conf to
remove/unset SPLUNK_OS_USER so that the software will retain
root privileges, and place backdoors under $SPLUNK_HOME/bin/,
etc. that will take malicious actions as user root the next
time Splunk is restarted.
4. Mitigation and Remediation Recommendation
The vendor has published a mitigation for this vulnerability
at: https://www.splunk.com/view/SP-CAAAP3M
5. Credit
This vulnerability was discovered by Hank Leininger of
KoreLogic, Inc.
6. Disclosure Timeline
2017.08.17 - KoreLogic submits vulnerability details to Splunk.
2017.08.17 - Splunk confirms receipt.
2017.08.22 - Splunk notifies KoreLogic that the issue has been
assigned an internal ticket and will be addressed.
2017.09.29 - 30 business days have elapsed since the vulnerability
was reported to Splunk.
2017.10.17 - KoreLogic requests an update from Splunk.
2017.10.18 - Splunk informs KoreLogic that they will issue an advisory
on October 28th.
2017.10.23 - 45 business days have elapsed since the vulnerability
was reported to Splunk.
2017.10.30 - Splunk notifies KoreLogic that the advisory is published.
2017.11.03 - KoreLogic public disclosure.
7. Proof of Concept
See 3. Technical Description.
The contents of this advisory are copyright(c) 2017
KoreLogic, Inc. and are licensed under a Creative Commons
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