Detection: Linux Possible GSM Privilege Escalation

Updated Date: 2026-07-08 ID: ae13064b-72ea-41fb-9d29-716c27e01208 Author: Raven Tait, Splunk Type: Anomaly Product: Splunk Enterprise Security

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.

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="*rmmod *"
 9Processes.process="*n_gsm*"
10Processes.process="*exec *"
11Processes.process IN (
12    "*/bin/bash*",
13    "*/bin/dash*",
14    "*/bin/sh*",
15    "*/bin/zsh*"
16)
17
18by Processes.process Processes.vendor_product
19   Processes.user_id Processes.process_hash Processes.parent_process_name Processes.parent_process_exec
20   Processes.action Processes.dest Processes.process_current_directory Processes.process_path
21   Processes.process_integrity_level Processes.original_file_name Processes.parent_process
22   Processes.parent_process_path Processes.parent_process_guid Processes.parent_process_id
23   Processes.process_guid Processes.process_id Processes.user Processes.process_name
24
25
26| `drop_dm_object_name(Processes)`
27
28| `security_content_ctime(firstTime)`
29
30| `security_content_ctime(lastTime)`
31
32| `linux_possible_gsm_privilege_escalation_filter`

Data Source

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

Macros Used

Name	Value
security_content_summariesonly	`summariesonly=`summariesonly_config `allow_old_summaries=`oldsummaries_config `fillnull_value=`fillnull_config``
linux_possible_gsm_privilege_escalation_filter	`search *`

linux_possible_gsm_privilege_escalation_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1068	Exploitation for Privilege Escalation	Privilege Escalation

Exploitation

DE.AE

CIS 10

CVE

CVE-2023-6546

Default Configuration

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

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Finding (Notable)	No
Creates Intermediate Finding (Risk Event)	Yes

Anomaly detections generate Intermediate Findings (Risk Events). They do not generate a Finding (Notable) directly.

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 administrators or developers testing GSM multiplexor configurations may trigger this detection. Filter based on known authorized users or testing environments.

Associated Analytic Story

Linux Privilege Escalation

Intermediate Findings

Message	Entity Field	Entity Type	Risk Score
Potential GSM Privilege Escalation via [$process$] by [$user$] on [$dest$].	dest	system	20

Threat Objects

Field	Type
process	process
process_name	process_name
parent_process_name	parent_process_name

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`Syslog:Linux-Sysmon/Operational`	`sysmon:linux`
Integration	✅ Passing	Dataset	`Syslog:Linux-Sysmon/Operational`	`sysmon:linux`

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