CVE-2023-6735 is a high severity (CVSS 8.8) local privilege escalation in the mk_tsm agent plugin of Checkmk, fixed in 2.2.0p18, 2.1.0p38 and 2.0.0p39. A user on a monitored host could gain root. Update the agent plugin, or disable the Tivoli Storage Manager plugin if you cannot.
What's affected
Checkmk lists the affected versions as 2.2.0, 2.1.0 and 2.0.0 (end of life) and older. The fix shipped in Checkmk 2.2.0p18, 2.1.0p38 and 2.0.0p39 per the CVE record, and the vendor note (Werk 16273) also lists 2.3.0b1. The weakness lives in the agent plugin that runs on monitored hosts, not in the central site.
The record's CPE entries only name 2.0.0 beta builds, so use the vendor advisory for the real range. The vendor rates the Werk level as Trivial while giving a CVSS score of 8.8. Both are in the advisory. The score is the number used here.
How to check if you're exposed
Find out whether the plugin is deployed. On Linux hosts the agent plugins normally live in a plugins directory under the agent's install path, so look for a file named mk_tsm there.
ls /usr/lib/check_mk_agent/plugins/ | grep -i mk_tsm
If the file exists, the host runs the plugin. Compare the agent version with the fixed releases above. In the Checkmk interface you can also review the agent version reported for each host.
What to do now
- Update Checkmk to a patched release for your series: 2.2.0p18, 2.1.0p38, 2.0.0p39 or newer.
- Redeploy agents so the fixed mk_tsm plugin reaches each host. The vendor marks this change as incompatible and says manual interaction might be required, so read Werk 16273 first.
- If you cannot update yet, disable the Tivoli Storage Manager plugin, which is the vendor's stated mitigation.
- Plan a move off the end-of-life 2.0.0 series.
Why it matters
Per the vendor, the plugin exploited insufficient quoting when using ksh's eval to build its environment. A crafted command line that shows up in the output of ps could then be interpreted as part of the script, giving a user on the monitored host root privileges. The fix removes the use of eval and corrects the quoting. The vendor says the issue was found during internal review.
The CVE record also tags CWE-95, improper neutralization of directives in dynamically evaluated code, and CWE-269, improper privilege management. Agents usually run as root because they need to read system state, so any shortcut in how they build commands is a privilege boundary.
Desktop and agent software is easy to miss because it sits outside the usual server patch cycle. Build a list of where it runs, push the update through your software deployment tool, and confirm the installed version afterward rather than trusting the job status.
Weakness class in the record: CWE-95 (Eval Injection) CWE-269 (Improper Privilege Management).
Try it yourself
Click through it at your own pace, or open it full screen.
Quick check
Does this affect the central Checkmk server?
The advisory describes an agent plugin on monitored hosts. Still update the server to a fixed release, since the agent plugins are shipped from it.
How do I confirm the fix landed?
Check the version on a sample of hosts after rollout and keep the output as evidence. Deployment tools can report success while some hosts miss the update.
Sources
Last reviewed: 19 October 2026.
