Key Takeaways
- Splunk Enterprise versions prior to 10.2.4 and 10.0.7 contain a critical unauthenticated file‑operation flaw (CVE‑2026-20253) rated 9.8 CVSS.
- The vulnerability resides in the PostgreSQL sidecar service endpoint, which lacks authentication checks.
- Exploitation can lead to arbitrary file creation/truncation and ultimately remote code execution (RCE).
- Patches are available in Splunk Enterprise 10.0.7 (for the 10.0.x line) and 10.2.4 (for the 10.2.x line); version 10.4 is unaffected.
- Splunk Cloud does not use the PostgreSQL sidecar and is therefore not impacted.
- Attackers can abuse the
/v1/postgres/recovery/backupand/v1/postgres/recovery/restoreendpoints to inject malicious SQL, achieve arbitrary file writes, and overwrite a Splunk‑executed Python script. - No public evidence of active exploitation exists, but the disclosed details increase the risk of opportunistic attacks.
- Immediate patching is strongly advised; organizations should also restrict network access to the sidecar endpoint and monitor for suspicious file changes.
Overview of CVE-2026-20253 and Severity
CVE‑2026-20253 is a high‑impact security flaw affecting Splunk Enterprise releases earlier than 10.0.7 and 10.2.4. The vulnerability earned a CVSS v3.1 base score of 9.8, reflecting its potential to allow unauthenticated remote attackers to perform arbitrary file operations and achieve remote code execution. The issue stems from missing authentication controls on a PostgreSQL sidecar service endpoint that ships with Splunk Enterprise. Because the endpoint is reachable over the network without credentials, any attacker who can contact the Splunk server can invoke its backup and restore functions. The severity rating underscores the urgency for administrators to apply the vendor‑supplied patches or implement mitigations promptly.
Affected Versions and Available Fixes
Splunk identified the specific release ranges that are vulnerable and the corresponding patched versions. For the 10.0.x series, releases 10.0.0 through 10.0.6 are affected, with the fix delivered in version 10.0.7. In the 10.2.x line, versions 10.2.0 through 10.2.3 are vulnerable, and the remedy appears in 10.2.4. Notably, Splunk Enterprise 10.4 does not contain the vulnerable sidecar component and is therefore immune. Splunk Cloud offerings remain safe because they do not employ the PostgreSQL sidecar architecture. Users running any of the affected builds should upgrade to the patched releases as soon as possible to eliminate the risk.
Technical Root Cause: Unauthenticated PostgreSQL Sidecar Endpoint
The core of the weakness lies in the PostgreSQL sidecar service that Splunk Enterprise uses for certain internal database operations. This sidecar exposes two HTTP endpoints—/v1/postgres/recovery/backup and /v1/postgres/recovery/restore—intended for internal backup and restore tasks. However, the implementation omitted any authentication or authorization checks, allowing any network‑reachable client to call these endpoints. Consequently, an unauthenticated attacker can trigger backup operations that write arbitrary files to the Splunk filesystem or initiate restore operations that load attacker‑supplied SQL into the local PostgreSQL instance. The lack of credential validation transforms a seemingly administrative feature into a potent entry point for compromise.
Exploitation Chain: Backup and Restore Abuse
WatchTowr Labs detailed a practical exploitation sequence that leverages the backup and restore endpoints to achieve pre‑authenticated remote code execution. First, the attacker connects to a PostgreSQL database under their control and uses the /backup endpoint to dump the database’s contents into a file of their choosing on the Splunk server. Next, they employ the /restore endpoint to load that dump into Splunk’s local PostgreSQL instance, supplying a passfile argument that points to the .pgpass file holding the password for the postgres_admin user. Because the restore process executes any SQL contained in the dumped database, the attacker can run arbitrary commands within Splunk’s PostgreSQL environment. This chain effectively bypasses authentication and gives the attacker a foothold inside the database layer.
Achieving Arbitrary File Write via lo_export
Once the attacker can execute arbitrary SQL, they invoke the PostgreSQL lo_export function, which extracts a large object (BLOB) from the database and writes it to a specified file path on the host filesystem. By crafting a database dump that defines a malicious function calling lo_export with a target path—such as a location within Splunk’s application directory—the attacker gains an arbitrary file write primitive. This capability allows them to create or overwrite any file accessible to the Splunk user account, including configuration files, logs, or executable scripts. The ability to write arbitrary files is a critical stepping stone toward full system compromise, as it enables the insertion of malicious code that will be trusted and executed by Splunk processes.
Path to Remote Code Execution: Overwriting a Python Script
With arbitrary file write in hand, the attacker selects a Python script that Splunk routinely executes as part of its modular input framework—for example, /opt/splunk/etc/apps/splunk_secure_gateway/bin/ssg_enable_modular_input.py. By overwriting this script with a payload (e.g., a reverse shell or command‑execution routine), the attacker ensures that the malicious code runs the next time Splunk invokes the script. Because the script runs under the Splunk service account, which typically possesses elevated privileges on the host, the attacker achieves remote code execution with the same privileges as the Splunk process. This final step transforms an initial unauthenticated file‑operation flaw into a complete compromise of the affected Splunk Enterprise server.
Mitigation and Remediation Guidance
Splunk’s advisory urges immediate upgrade to the patched versions (10.0.7 or 10.2.4) as the primary mitigation. Organizations unable to apply the updates right away should consider network‑level controls: restrict access to the PostgreSQL sidecar endpoint (typically on port 8089) to trusted management hosts only, and employ firewall rules to block external traffic to the /v1/postgres/recovery/* URLs. Additionally, enabling audit logging for file‑system changes and monitoring for unexpected modifications to Splunk‑owned Python scripts can help detect exploitation attempts. Regular vulnerability scanning and adherence to the principle of least privilege for service accounts further reduce the attack surface.
Current Threat Landscape and Recommendations
At present, there are no publicly confirmed instances of CVE‑2026-20253 being exploited in the wild. However, the detailed technical disclosure by watchTowr Labs increases the likelihood that threat actors will develop and deploy exploit scripts targeting unpatched Splunk Enterprise installations. Historical trends show that once critical CVSS‑scored vulnerabilities are disclosed with proof‑of‑concept details, opportunistic attacks often follow within days or weeks. Therefore, administrators should treat this issue as time‑sensitive: prioritize patching, verify that the correct version is running, and conduct post‑patch validation to ensure the sidecar endpoint now requires authentication. Maintaining an up‑to‑date asset inventory and subscribing to vendor security alerts will help organizations stay ahead of similar threats in the future.