CVE-2026-20253 Overview
CVE-2026-20253 is an authentication flaw in Splunk Enterprise and Splunk Cloud Platform. The PostgreSQL sidecar service endpoint lacks authentication controls. An unauthenticated, network-reachable attacker can create or truncate arbitrary files on the host.
The weakness maps to [CWE-306] Missing Authentication for Critical Function. Affected releases include Splunk Enterprise versions below 10.2.4 and 10.0.7, and Splunk Cloud Platform versions below 10.4.2604.3 and 10.2.2510.14. Splunk documented the issue in Splunk Security Advisory SVD-2026-0603.
Critical Impact
Unauthenticated attackers can create or truncate files on Splunk hosts, enabling configuration tampering, log destruction, and potential pathways to remote code execution.
Affected Products
- Splunk Enterprise versions below 10.2.4
- Splunk Enterprise versions below 10.0.7
- Splunk Cloud Platform versions below 10.4.2604.3 and 10.2.2510.14
Discovery Timeline
- 2026-06-10 - CVE-2026-20253 published to NVD
- 2026-06-10 - Last updated in NVD database
Technical Details for CVE-2026-20253
Vulnerability Analysis
The vulnerability resides in a PostgreSQL sidecar service shipped with affected Splunk versions. The sidecar exposes a network-accessible endpoint that invokes file operations on the underlying host. The endpoint does not verify caller identity or authorization before executing those operations.
An attacker who can reach the service over the network can request file creation or truncation against arbitrary paths. Truncating files clears their contents to zero bytes, while file creation can produce attacker-controlled artifacts on disk. Both primitives undermine the integrity and availability of the Splunk deployment.
The issue is reachable over the network, requires no privileges, and needs no user interaction, consistent with the published CVSS vector.
Root Cause
The root cause is missing authentication on a critical function [CWE-306]. The sidecar endpoint accepts file-operation requests without validating credentials, session tokens, or peer identity. Any process able to send traffic to the service port can invoke its functionality.
Attack Vector
Exploitation proceeds by sending crafted HTTP or service-protocol requests to the PostgreSQL sidecar endpoint. The attacker supplies a target file path and the desired operation. The service performs the create or truncate action under the privileges of the sidecar process, bypassing Splunk role-based access controls entirely. Refer to Splunk Security Advisory SVD-2026-0603 for vendor-published technical details.
Detection Methods for CVE-2026-20253
Indicators of Compromise
- Unexpected zero-byte files in Splunk configuration, index, or log directories indicating truncation activity.
- New files appearing in Splunk-managed paths without corresponding administrative actions in audit logs.
- Inbound network connections to the PostgreSQL sidecar service port from untrusted sources.
Detection Strategies
- Monitor process and file-system telemetry on Splunk hosts for write or truncate operations originating from the PostgreSQL sidecar process targeting non-database paths.
- Alert on network connections to the sidecar endpoint from outside the documented Splunk component IP ranges.
- Compare file integrity baselines for $SPLUNK_HOME configuration files and flag size changes to zero.
Monitoring Recommendations
- Forward host audit logs and Splunk internal logs to a centralized analytics platform for correlation.
- Track Splunk version inventory and flag deployments below the patched releases.
- Review firewall and segmentation logs for unexpected exposure of internal Splunk service ports.
How to Mitigate CVE-2026-20253
Immediate Actions Required
- Upgrade Splunk Enterprise to 10.2.4 or 10.0.7 or later as specified in the vendor advisory.
- Confirm Splunk Cloud Platform instances are running 10.4.2604.3, 10.2.2510.14, or later.
- Restrict network access to the PostgreSQL sidecar endpoint to trusted Splunk components only.
- Audit Splunk hosts for unexpected zero-byte files or unauthorized new files.
Patch Information
Splunk addressed the missing authentication issue in Splunk Enterprise 10.2.4 and 10.0.7, and in Splunk Cloud Platform 10.4.2604.3 and 10.2.2510.14. See Splunk Security Advisory SVD-2026-0603 for upgrade guidance and component-specific instructions.
Workarounds
- Apply network access controls so only authorized Splunk processes can reach the PostgreSQL sidecar port.
- Place Splunk indexers and search heads behind segmented internal networks with explicit allow-lists.
- If patching is delayed, monitor host-level file activity for the sidecar process and treat any non-database file write as suspicious.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
