🚨 CVE-2026-20253 - Critical Splunk Enterprise Unauthenticated File Creation Vulnerability

Unauthenticated arbitrary file creation and truncation vulnerability affecting Splunk Enterprise and Splunk Cloud Platform.

📖 Executive Summary

CVE-2026-20253 is a critical vulnerability in Splunk Enterprise and Splunk Cloud Platform that allows an unauthenticated remote attacker to create or truncate arbitrary files through an exposed PostgreSQL sidecar service endpoint.

Because the vulnerable functionality lacks authentication controls, attackers can perform file operations without valid credentials.

Successful exploitation may result in:

• Arbitrary file creation
• File truncation
• Data destruction
• Service disruption
• Potential privilege escalation
• Potential system compromise

🎯 Vulnerability Information

📸 Demo

🔥 Technical Overview

The vulnerability exists within a PostgreSQL sidecar service component that exposes sensitive file operation functionality.

Due to missing authentication checks:

Remote User
        │
        ▼
Accessible Sidecar Endpoint
        │
        ▼
Create Arbitrary Files
        │
        ▼
Truncate Existing Files
        │
        ▼
System Impact

An attacker only needs network access to the exposed service.

⚔️ Attack Flow

Attacker
    │
    ▼
Locate Exposed Splunk Service
    │
    ▼
Connect To PostgreSQL Sidecar
    │
    ▼
Unauthenticated Request
    │
    ▼
Create/Overwrite Files
    │
    ▼
Service Disruption
    │
    ▼
Potential Escalation

💥 Impact Analysis

Confidentiality

Potential exposure of sensitive operational data.

Integrity

Arbitrary file modification can compromise system integrity.

Availability

Critical files may be truncated, causing outages.

Operational Risk

SIEM infrastructure may become unreliable or unavailable.

🖥️ Affected Products

Splunk Enterprise

Splunk Cloud Platform

✅ Fixed Versions

📊 CVSS Breakdown

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

🔍 Exposure Assessment

Internet-Facing Splunk

Common ports:

8000
8089
8191
5432

Asset Discovery

Shodan

http.title:"Splunk"

product:"Splunk"

http.html:"Splunk"

FOFA

title="Splunk"

body="Splunk"

app="Splunk"

ZoomEye

app:"Splunk"

🛡️ Detection Guidance

Investigate

Unexpected:

File creation events
File truncation events
Service failures
Configuration changes
Database sidecar access

Linux Monitoring

find /opt/splunk -mtime -1

find /opt/splunk -size 0

journalctl -xe

grep -Ri "postgres" /opt/splunk/var/log/

🎯 Threat Hunting

Look for:

Unexpected empty files
Modified configuration files
Splunk restart anomalies
Unauthorized service access
Network connections to sidecar components

Potential targets:

server.conf
inputs.conf
outputs.conf
authentication.conf
web.conf

🔬 Reproduction Overview

1. Discover vulnerable Splunk instance
2. Reach PostgreSQL sidecar endpoint
3. Submit crafted request
4. Create or truncate target file
5. Observe system impact

⚠️ Weaponized exploit code is intentionally omitted.

🚑 Mitigation

Immediate Actions

Upgrade

10.2.4+
10.0.7+

Restrict Access

VPN-only access
Internal management network
ACL restrictions
Firewall filtering

Monitor

File creation activity
Configuration modifications
Unexpected service restarts

Hardening Recommendations

Network Segmentation

Management Interfaces
        │
        ├── Internal VLAN
        ├── VPN Access
        └── Zero Trust Controls

Logging

Enable:

Auditd
Sysmon for Linux
EDR telemetry
Network monitoring

📈 Threat Landscape

Why this vulnerability matters:

Splunk Often Contains

• Security logs
• Authentication records
• Incident response data
• SIEM analytics
• Threat intelligence feeds

Compromising Splunk can significantly impact an organization's ability to detect attacks.

📁 Repository Structure

CVE-2026-20253/
│
├── README.md
│
├── assets/
│   ├── CVE-2026-20253.png
│   └── screenshots/
│
├── advisory/
│   ├── technical-analysis.md
│   ├── attack-surface.md
│   └── patch-guidance.md
│
├── detection/
│   ├── sigma/
│   ├── yara/
│   ├── splunk-searches/
│   └── hunting-guide.md
│
├── iocs/
│   └── indicators.md
│
└── references/
    └── links.md

📚 References

Vendor Resources

• Splunk Security Advisory
• Splunk Security Vulnerability Disclosure Program

Databases

• MITRE CVE
• NIST NVD
• CISA KEV (if added)

Related Weaknesses

• CWE-306: Missing Authentication for Critical Function

⚠️ Disclaimer

This repository is intended solely for:

• Security research
• Defensive operations
• Threat intelligence
• Incident response
• Vulnerability management

All testing should be performed only against systems you own or are explicitly authorized to assess.

🚨 PATCH IMMEDIATELY

CVE-2026-20253

Splunk Enterprise • Critical • CVSS 9.8

Defend • Detect • Patch