CVE-2026-20253: Splunk Enterprise Missing Authentication for Critical Function Vulnerability

Splunk Enterprise contains a missing authentication vulnerability that lets an unauthenticated user reach a PostgreSQL sidecar service endpoint and create or truncate arbitrary files. The issue is tracked as CVE-2026-20253 and is classified under CWE-306. Organizations that rely on Splunk for centralized logging and security monitoring should determine whether their deployments expose the affected component.

How it works

The weakness is missing authentication for a critical function. An attacker can send requests directly to the PostgreSQL sidecar service endpoint without presenting credentials. Because the endpoint lacks an authentication check, the request succeeds and the server performs file operations on behalf of the unauthenticated caller.

• The CWE-306 condition means the code path assumes the caller has already been authorized when no such check exists.
• Successful abuse results in creation or truncation of files on the host running the sidecar service.
• No further details on request format or payload are provided in the available summary; confirm mechanics against the vendor advisory.

Am I affected? How to find it in your systems

Splunk Enterprise deployments that include the PostgreSQL sidecar service are potentially exposed. Inventory all Splunk search heads, indexers, and clustered nodes to identify where the sidecar component is present. Review configuration files and service definitions that reference the PostgreSQL sidecar endpoint. Check installed Splunk versions and any custom integrations that expose the endpoint to untrusted networks. Examine logs for unexpected file operations or unauthenticated connections to the sidecar port; absence of such logs does not rule out prior activity.

• Confirm exact affected versions and configurations against the vendor advisory before declaring systems safe.
• Map network exposure of the sidecar service as part of the inventory.

How to remediate

Apply the vendor-supplied update or configuration change that restores authentication on the PostgreSQL sidecar endpoint. Follow the instructions published in the official Splunk advisory. Ensure the change is deployed consistently across all search heads, indexers, and forwarders that run the sidecar service. After patching, verify that the endpoint now requires authentication and that file-creation privileges are restricted to authorized accounts.

• Document the patch deployment for each asset to satisfy BOD 26-04 tracking requirements.
• Re-scan the environment to confirm the sidecar service no longer accepts unauthenticated requests.

If you can't patch immediately

Until the vendor fix can be applied, reduce the attack surface by restricting network access to the PostgreSQL sidecar endpoint through firewall rules or network segmentation. Disable or remove the sidecar service where it is not required. Monitor authentication and file-system logs for anomalous activity on Splunk hosts. For cloud-hosted instances, follow the additional guidance in CISA BOD 26-04; if mitigations cannot be implemented, discontinue use of the affected deployment.

• Virtual patching or web-application firewall rules may be considered only after confirming they address the specific unauthenticated endpoint.
• Continue to track the asset in the BOD 26-04 inventory until remediation is complete.

If your data may have been exposed

Successful exploitation can alter files on Splunk hosts and may indicate broader compromise. Review file-integrity monitoring data and Splunk internal logs for unexpected changes. Organizations can run a free exposure scan of their email addresses against known breach data to check for related incidents.