Detection: Linux Possible Nimbuspwn Privilege Escalation

Description

The following analytic detects directory traversal attempts associated with Nimbuspwn, a Linux privilege escalation vulnerability affecting the networkd-dispatcher service. Nimbuspwn exploits weaknesses in the networkd-dispatcher service to traverse directories and execute arbitrary code with elevated privileges. If confirmed malicious, this activity could allow an attacker to escalate privileges to root, potentially leading to full system compromise, persistent unauthorized access, and the ability to deploy additional malicious payloads.

Search

 1
 2| tstats `security_content_summariesonly`
 3  count min(_time) as firstTime
 4        max(_time) as lastTime
 5
 6from datamodel=Endpoint.Processes where
 7
 8Processes.process="*networkd-dispatcher*"
 9Processes.process="*../*"
10
11by Processes.process Processes.vendor_product Processes.user_id
12   Processes.process_hash Processes.parent_process_name Processes.parent_process_exec
13   Processes.action Processes.dest Processes.process_current_directory Processes.process_path
14   Processes.process_integrity_level Processes.original_file_name Processes.parent_process
15   Processes.parent_process_path Processes.parent_process_guid Processes.parent_process_id
16   Processes.process_guid Processes.process_id Processes.user Processes.process_name
17
18
19| `drop_dm_object_name(Processes)`
20
21| `security_content_ctime(firstTime)`
22
23| `security_content_ctime(lastTime)`
24
25| `linux_possible_nimbuspwn_privilege_escalation_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon for Linux EventID 1	Linux	'sysmon:linux'	'Syslog:Linux-Sysmon/Operational'

Macros Used

Annotations

CVE

• CVE-2022-29799

• CVE-2022-29800

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Implementation

The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the Processes node of the Endpoint data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.

Known False Positives

Legitimate system processes or administrative scripts that traverse directories in a similar pattern may trigger this detection. Filter based on known administrative activity and verified system processes.

Associated Analytic Story

• Linux Post-Exploitation

• Linux Privilege Escalation

• Linux Persistence Techniques

Finding

Threat Objects

References

• https://www.microsoft.com/security/blog/2022/04/26/microsoft-finds-new-elevation-of-privilege-linux-vulnerability-nimbuspwn/

Detection Testing

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub |

Version: 1