Splunk Enterprise Authentication Bypass Vulnerability

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What is the Attack?

A critical authentication bypass vulnerability, CVE-2026-20253 (CVSS 9.8), affects Splunk Enterprise versions 10.0.x and 10.2.x. The flaw stems from missing authentication on a PostgreSQL sidecar service endpoint, allowing an unauthenticated attacker to create or truncate arbitrary files on a vulnerable server.

Security researchers have demonstrated that the vulnerability can be leveraged toward pre-authentication remote code execution (RCE) under certain conditions, and active exploitation has been confirmed. The vulnerability has been added to CISA’s Known Exploited Vulnerabilities (KEV) Catalog, making it a high-priority patching target for organizations running exposed Splunk Enterprise instances.

An attacker who successfully exploits CVE-2026-20253 may be able to:

• Create or truncate arbitrary files on the target server.

• Bypass authentication protections.

• Potentially achieve pre-authentication remote code execution.

• Disrupt Splunk services.

What is the recommended Mitigation?

Affected:

Splunk Enterprise 10.2 prior to 10.2.4

Splunk Enterprise 10.0 prior to 10.0.7

Upgrade to:

Splunk Enterprise 10.2.4 or later

Splunk Enterprise 10.0.7 or later

If immediate patching is not possible:

• Disable the PostgreSQL sidecar service as recommended by Splunk.

• Restrict network access to Splunk management interfaces.

• Monitor for unexpected file creation or service behavior.

• Review logs for suspicious unauthenticated access attempts.

What FortiGuard Coverage is available?

• FortiGuard IPS provides protection against exploit attempts targeting vulnerable services.

• FortiGuard Web Filtering blocks access to known malicious infrastructure used during exploitation.

• FortiGuard AntiVirus detects and blocks malware payloads delivered following successful exploitation.

• FortiEDR detects suspicious post-exploitation behavior, including unauthorized file modifications and persistence techniques.

• FortiGuard Incident Response Service assists organizations in investigating and determining the scope of compromise, and supporting remediation efforts following exploitation.