The Collector Service in SolarWinds Orion Platform before 2020.2.4 uses MSMQ (Microsoft Message Queue) and doesn't set permissions on its private queues. As a result, remote unauthenticated clients can send messages to TCP port 1801 that the Collector Service will process. Additionally, upon processing of such messages, the service deserializes them in insecure manner, allowing remote arbitrary code execution as LocalSystem.

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-25274
• https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/full-system-control-with-new-solarwinds-orion-based-and-serv-u-ftp-vulnerabilities/