A critical vulnerability chain has been identified in Splunk Enterprise, enabling unauthenticated attackers to execute remote code through a misconfigured PostgreSQL sidecar service. This flaw, designated as CVE-2026-20253 with a CVSS score of 9.8, affects Splunk Enterprise versions 10 and later.
The issue originates from the PostgreSQL Sidecar Service, an internal component introduced in recent Splunk versions. While this service is not always active in on-premise deployments, it is enabled by default in Splunk Enterprise on AWS, making cloud-based instances particularly vulnerable.
Exploitation Details
Security researchers discovered that the vulnerable service, although listening on localhost, can be accessed externally via Splunk’s main web interface. Attackers can send crafted HTTP requests to internal API endpoints such as /v1/postgres/recovery/backup and /restore through the Splunk web service running on port 8000.
The core issue lies in the absence of proper authentication controls. The API accepts any credentials, including empty values, and forwards them to backend PostgreSQL utilities like pg_dump and pg_restore. These tools are executed without enforcing authentication checks, allowing attackers to trigger database operations without valid access.
Initially, the vulnerability appeared limited to arbitrary file creation and truncation. By manipulating the backupFile parameter, attackers can write files to arbitrary locations on the system using directory traversal techniques. However, researchers discovered a more severe impact by chaining multiple behaviors.
By injecting a PostgreSQL connection string into the database parameter, attackers can override default connection settings and force Splunk to connect to an attacker-controlled database. This allows malicious database content to be written to the Splunk filesystem.
Furthermore, Splunk’s restore feature can use credentials stored in a local .pgpass file, enabling attackers to abuse exposed database credentials during restore operations. By leveraging this file, attackers can authenticate to the internal PostgreSQL instance and execute arbitrary SQL during the restore process.
Researchers demonstrated that specially crafted SQL payloads can write attacker-controlled files to disk using PostgreSQL large object export functions. This primitive enables full arbitrary file write access under the Splunk user.
With file write access, achieving remote code execution becomes straightforward. In the proof-of-concept, attackers overwrote a legitimate Splunk Python script that is executed during normal operations, allowing them to execute system commands and confirm code execution on the target system.
Implications and Recommendations
This vulnerability underscores the risks associated with internal services exposed through proxy mechanisms, especially when authentication is inconsistently enforced. Organizations using Splunk Enterprise, particularly those with cloud deployments, should prioritize applying the latest security patches and reviewing their configurations to ensure that internal services are not inadvertently exposed.
Administrators are advised to disable the PostgreSQL Sidecar Service if it is not required and to implement strict access controls to prevent unauthorized access. Regular security audits and penetration testing can help identify and mitigate such vulnerabilities before they can be exploited by malicious actors.
As cyber threats continue to evolve, maintaining a proactive security posture is essential. Organizations should stay informed about emerging vulnerabilities and apply timely updates to protect their systems and data from potential breaches.
