Splunk Enterprise PostgreSQL Sidecar Service Arbitrary File Write Vulnerability

Splunk has disclosed CVE-2026-20253, a critical unauthenticated arbitrary file write vulnerability affecting Splunk Enterprise. The flaw exists in a PostgreSQL sidecar service endpoint that lacks authentication controls, allowing a network-reachable attacker to create or truncate arbitrary files on the underlying host without credentials. The vulnerability carries a CVSS v3.1 score of 9.8 and could lead to denial of service, loss of log integrity, or, under certain conditions, remote code execution.

Technical Details

CVE-2026-20253 is caused by missing authentication on PostgreSQL sidecar service endpoints within affected Splunk Enterprise deployments. An attacker who can reach the service over the network can invoke file operations without supplying valid credentials.

Key facts:

• CVSS v3.1: 9.8 (Critical)
• CWE-306: Missing Authentication for Critical Function
• No authentication required
• Network exploitable
• User interaction not required
• Successful exploitation allows arbitrary file creation or truncation on the host system

Researchers have demonstrated that the file write primitive may be chained into remote code execution by overwriting files that are later executed by Splunk services.

Organizations relying on Splunk for SIEM, threat detection, compliance reporting, and log retention should treat this vulnerability as high priority because compromise of the logging platform can directly impact detection, investigation, and audit capabilities.

Stop Guessing, Start Proving