Detection: Splunk RCE PDFgen Render

Updated Date: 2024-07-01 ID: bc2b7437-0400-438b-9537-21ab5b7d2d53 Author: Rod Soto, Chase Franklin Type: TTP Product: Splunk Enterprise Security

Description

This is a hunting search designed to find and discover exploitation attempts against Splunk pdfgen render endpoint which results in remote

1index=_internal sourcetype=splunk_pdfgen _raw IN ("*base64*", "*lambda*", "*system*") 
2| stats count min(_time) as firstTime max(_time) as lastTime by index, sourcetype, host, _raw 
3| `security_content_ctime(firstTime)` 
4| `security_content_ctime(lastTime)` 
5| `splunk_rce_pdfgen_render_filter`

Data Source

Name Platform Sourcetype Source Supported App
Splunk Splunk icon Splunk 'splunkd_ui_access' 'splunkd_ui_access.log' N/A

Macros Used

Name Value
security_content_ctime convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)
splunk_rce_pdfgen_render_filter search *
splunk_rce_pdfgen_render_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
T1210 Exploitation of Remote Services Lateral Movement
KillChainPhase.EXPLOITAITON
NistCategory.DE_CM
Cis18Value.CIS_10
APT28
Dragonfly
Earth Lusca
FIN7
Fox Kitten
MuddyWater
Threat Group-3390
Tonto Team
Wizard Spider
menuPass

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 Notable Yes
Rule Title %name%
Rule Description %description%
Notable Event Fields user, dest
Creates Risk Event True
This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

Requires access to internal indexes.

Known False Positives

This search will hunt for exploitation attempts against Splunk PDFgen render function, and not all requests are necesarily malicious so there will be false positives.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
Possible exploitation against $host$ 80 80 100
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset /opt/splunk/var/log/splunk/pdfgen.log splunk_pdfgen
Integration ✅ Passing Dataset /opt/splunk/var/log/splunk/pdfgen.log splunk_pdfgen

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