Linux Possible GSM Privilege Escalation

Name:Linux Possible GSM Privilege Escalation
id:ae13064b-72ea-41fb-9d29-716c27e01208
version:1
date:None
author:Raven Tait, Splunk
status:production
type:Anomaly
Description:The following analytic detects the commands used in a race condition found in the GSM 0710 tty multiplexor in the Linux kernel. This issue occurs when two threads execute the GSMIOC_SETCONF ioctl on the same tty file descriptor with the gsm line discipline enabled. This could allow a local unprivileged user to escalate their privileges on the system.
Data_source:

• -Sysmon for Linux EventID 1

search:| tstats `security_content_summariesonly`
count min(_time) as firstTime
max(_time) as lastTime

from datamodel=Endpoint.Processes where

Processes.process="*rmmod *"
Processes.process="*n_gsm*"
Processes.process="*exec *"
Processes.process IN (
"*/bin/bash*",
"*/bin/dash*",
"*/bin/sh*",
"*/bin/zsh*"
)

by Processes.process Processes.vendor_product
Processes.user_id Processes.process_hash Processes.parent_process_name Processes.parent_process_exec
Processes.action Processes.dest Processes.process_current_directory Processes.process_path
Processes.process_integrity_level Processes.original_file_name Processes.parent_process
Processes.parent_process_path Processes.parent_process_guid Processes.parent_process_id
Processes.process_guid Processes.process_id Processes.user Processes.process_name

| `drop_dm_object_name(Processes)`
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `linux_possible_gsm_privilege_escalation_filter`

how_to_implement: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 administrators or developers testing GSM multiplexor configurations may trigger this detection. Filter based on known authorized users or testing environments.
References:
  -https://access.redhat.com/security/cve/cve-2023-6546
  -https://github.com/Nassim-Asrir/ZDI-24-020/
drilldown_searches:
 earliest_offset:'$info_min_time$'
 latest_offset:'$info_max_time$'
 name:'View the detection results for - "$user$" and "$dest$"'
 search:'%original_detection_search% | search user = "$user$" dest = "$dest$"'
 name:'View risk events for the last 7 days for - "$user$" and "$dest$"'
 search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$", "$dest$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
 earliest_offset:'7d'
 latest_offset:'0'
analytic_story:['Linux Privilege Escalation']

asset_type:Endpoint

mitre_attack_id:['T1068']

product:['Splunk Enterprise', 'Splunk Enterprise Security', 'Splunk Cloud']

category:endpoint

security_domain:endpoint

tags:

tests:
 name:'True Positive Test'
 test_type:'unit'
 attack_data:
  data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1068/linux_possible_linux_gsm_privilege_escalation/snapattack_linux.log
  source: Syslog:Linux-Sysmon/Operational
  sourcetype: sysmon:linux
manual_test:None