CVE-2025-34274 is a critical weakness (CVSS 9.8) in Nagios Log Server, which ran its embedded Logstash process as the root user. A compromise of Logstash would then give an attacker root. Versions before 2024R2.0.3 are affected. Upgrade to 2024R2.0.3 or later, where Logstash runs as the lower privileged nagios user.
What's affected
The record lists Nagios Log Server versions prior to 2024R2.0.3 as affected. The vendor change described in the record is that the Logstash service now runs as the 'nagios' user instead of root.
This entry is different from a classic bug. No specific exploit is described. The issue is that a network facing service that accepts untrusted input and can load third party plugins ran with more privilege than it needed. The record gives examples of how Logstash could be compromised: an insecure plugin, injection into a pipeline configuration, or a flaw in input parsing.
How to check if you're exposed
Check the installed version in the Log Server web interface. Anything before 2024R2.0.3 is affected.
You can also see which account runs the process. On the Log Server host, list processes and look at the user column for Logstash:
ps -eo user,pid,args | grep -i [l]ogstash
If the first column shows root, the process has the excess privilege the advisory describes. After the upgrade the same command should show the nagios user. Treat that output as a quick sanity check, and rely on the vendor release notes for the authoritative change.
Also review which Logstash plugins and pipeline files you added yourself. Custom inputs and third party plugins widen what an attacker could reach.
What to do now
- Upgrade Nagios Log Server to 2024R2.0.3 or later on every node.
- After the upgrade, confirm that Logstash runs as the nagios user and that your inputs and outputs still work, since file permissions can matter when a service stops running as root.
- Remove plugins you do not use, and review the origin of the ones you keep.
- Limit who can edit pipeline configuration, and who can reach the ports Logstash listens on.
- Review the Nagios changelog and security disclosures for other Log Server fixes that apply to your branch.
Why it matters
The class is CWE-250 (Execution with Unnecessary Privileges). It is a defense in depth failure. The code may be fine today, but running as root means every future bug in an input parser, codec or plugin becomes a full system compromise instead of a limited one. Logstash is built to ingest data from many sources, which makes it a natural place for malformed input to arrive.
The fix reduces blast radius. It does not remove the chance that Logstash is attacked, so it works best alongside network restrictions on inbound log sources. The record does not mark this CVE as listed in CISA KEV.
Quick check
Is there a known exploit for this?
The record describes a privilege design problem and does not describe an exploit. It is not flagged as exploited in the CISA KEV catalog.
Will anything break when Logstash stops running as root?
It can, if inputs read files or bind ports that only root could use. Test after upgrading and follow the vendor release notes.
Sources
Last reviewed: 18 October 2026.
