Detection: Splunk Unauthenticated Log Injection Web Service Log

Updated Date: 2024-10-17 ID: de3908dc-1298-446d-84b9-fa81d37e959b Author: Rod Soto Type: Hunting Product: Splunk Enterprise Security

Description

The following analytic identifies potential log injection attempts into the Splunk server via specially crafted web URLs. It detects ANSI escape codes within the uri_path field of splunkd_webx logs. This activity is significant as it can lead to log file manipulation, potentially obfuscating malicious actions or misleading analysts. If confirmed malicious, an attacker could manipulate log files to hide their tracks or execute further attacks, compromising the integrity of the logging system and making incident response more challenging.

Search

1`splunkd_webx`  uri_path IN ("*\x1B*", "*\u001b*", "*\033*", "*\0x9*", "*\0x8*") 
2| stats count by uri_path method host status clientip 
3| `splunk_unauthenticated_log_injection_web_service_log_filter`

Data Source

Name	Platform	Sourcetype	Source
Splunk	Splunk	`'splunkd_ui_access'`	`'splunkd_ui_access.log'`

Macros Used

Name	Value
splunkd_webx	`index=_internal sourcetype=splunk_web_access`
splunk_unauthenticated_log_injection_web_service_log_filter	`search *`

splunk_unauthenticated_log_injection_web_service_log_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
T1190	Exploit Public-Facing Application	Initial Access

KillChainPhase.DELIVERY

NistCategory.DE_AE

Cis18Value.CIS_10

APT28

APT29

APT39

APT41

APT5

Agrius

Axiom

BackdoorDiplomacy

BlackTech

Blue Mockingbird

Cinnamon Tempest

Dragonfly

Earth Lusca

Ember Bear

FIN13

FIN7

Fox Kitten

GALLIUM

GOLD SOUTHFIELD

HAFNIUM

INC Ransom

Ke3chang

Kimsuky

Magic Hound

Moses Staff

MuddyWater

Play

Rocke

Sandworm Team

Threat Group-3390

ToddyCat

Volatile Cedar

Volt Typhoon

Winter Vivern

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 Risk Event	False

This configuration file applies to all detections of type hunting.

Implementation

This only affects web enabled Splunk instances. The detection does require the ability to search the _internal index.

Known False Positives

This hunting search will produce false positives if ANSI escape characters are included in URLs either voluntarily or by accident. This search will not detect obfuscated ANSI characters.

Associated Analytic Story

Splunk Vulnerabilities

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
Possible Splunk unauthenticated log injection web service log exploitation attempt against $host$ from $clientip$	9	30	30

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

https://advisory.splunk.com/advisories/SVD-2023-0606

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`/opt/splunk/var/log/splunk/web_access.log`	`splunk_web_access`
Integration	✅ Passing	Dataset	`/opt/splunk/var/log/splunk/web_access.log`	`splunk_web_access`

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: 3