Splunk has released urgent security updates to address a critical vulnerability in Splunk Enterprise that could allow attackers to perform unauthorized file operations and potentially achieve remote code execution (RCE) without authentication.
Tracked as CVE-2026-20253, the flaw carries a CVSS score of 9.8, making it one of the most severe vulnerabilities disclosed for the platform.
Unauthenticated File Operations Through PostgreSQL Sidecar Service
According to Splunk, the vulnerability affects specific versions of Splunk Enterprise where a PostgreSQL sidecar service endpoint lacks proper authentication controls.
“An unauthenticated user could create or truncate arbitrary files through a PostgreSQL sidecar service endpoint,” Splunk stated in its security advisory.
Because the vulnerable endpoint does not require authentication, any attacker with network access to the affected system could potentially trigger file operations without valid credentials.
Affected Versions
The vulnerability impacts the following Splunk Enterprise releases:
- Splunk Enterprise 10.0.0 – 10.0.6 (Fixed in 10.0.7)
- Splunk Enterprise 10.2.0 – 10.2.3 (Fixed in 10.2.4)
Not Affected
- Splunk Enterprise 10.4
- Splunk Cloud
Splunk noted that Splunk Cloud remains unaffected because the product does not utilize PostgreSQL sidecars.
Technical Details Released by Researchers
Security researchers at watchTowr Labs published additional technical analysis of CVE-2026-20253, revealing how the flaw could be leveraged for pre-authentication remote code execution through the following endpoints:
/v1/postgres/recovery/backup/v1/postgres/recovery/restore
The researchers demonstrated that attackers could abuse these endpoints to manipulate PostgreSQL backup and restore operations, eventually gaining the ability to write arbitrary files to the underlying file system.
How the Attack Works
The attack chain involves several steps:
- An attacker connects the vulnerable Splunk instance to a malicious, attacker-controlled PostgreSQL database.
- Using the vulnerable
/backupendpoint, the attacker creates a database dump and writes it to an arbitrary location on the Splunk server. - The
/restoreendpoint is then used to import the malicious database dump into the local PostgreSQL instance. - During the restoration process, attacker-controlled SQL commands are executed.
- These SQL commands can leverage PostgreSQL functions such as
lo_exportto write arbitrary files to the system.
Researchers explained that once they were able to restore attacker-controlled SQL into the local PostgreSQL instance, creating a controlled file-write primitive became straightforward.
From File Write to Remote Code Execution
The arbitrary file-write capability significantly increases the severity of the vulnerability.
An attacker could overwrite Python scripts that Splunk routinely executes, such as:
/opt/splunk/etc/apps/splunk_secure_gateway/bin/ssg_enable_modular_input.py
By replacing legitimate code with a malicious payload, attackers could achieve full remote code execution on the affected server.
Complete Exploitation Chain
The demonstrated proof-of-concept attack follows these stages:
- Create a specially crafted PostgreSQL database.
- Configure authentication settings to permit access without a password.
- Grant privileges required to execute functions such as
lo_export. - Use the vulnerable backup endpoint to place a malicious database dump on the Splunk file system.
- Trigger the restore endpoint to execute attacker-controlled SQL.
- Write a malicious Python script to disk.
- Wait for Splunk to execute the modified script, resulting in remote code execution.
No Active Exploitation Reported Yet
At the time of disclosure, there is no evidence that CVE-2026-20253 has been exploited in real-world attacks. However, the publication of detailed technical information and proof-of-concept exploitation methods significantly increases the likelihood of threat actors attempting to weaponize the flaw.
Organizations running affected versions of Splunk Enterprise are strongly advised to upgrade immediately to:
- Splunk Enterprise 10.0.7
- Splunk Enterprise 10.2.4
Prompt patching is critical to prevent potential compromise of Splunk environments and the sensitive security data they often contain.
Final Thoughts
With a CVSS score of 9.8 and a viable path from unauthenticated access to remote code execution, CVE-2026-20253 represents a high-priority security risk for Splunk Enterprise users. Security teams should review their deployments, apply the latest patches, and monitor systems for any suspicious activity related to PostgreSQL backup and restore operations.
