Splunk has released important security updates to fix a critical vulnerability in Splunk Enterprise that could allow attackers to perform unauthorized file operations and potentially execute malicious code on vulnerable systems without needing any authentication.
The vulnerability, identified as CVE-2026-20253, has received a CVSS score of 9.8, making it one of the most severe security issues affecting the platform. Security experts are urging organizations using affected versions of Splunk Enterprise to apply the latest patches immediately to prevent potential attacks.
According to Splunk, the flaw exists in a PostgreSQL sidecar service used within Splunk Enterprise. Due to missing authentication controls, any attacker who can reach the vulnerable service over a network can interact with specific endpoints without providing valid credentials.
The company stated that unauthenticated users could create or overwrite arbitrary files through the PostgreSQL sidecar service endpoint. This weakness opens the door to more serious attacks, including remote code execution (RCE), which allows attackers to run malicious commands on targeted systems.
The issue affects the following versions of Splunk Enterprise:
- Splunk Enterprise 10.0.0 through 10.0.6 – Fixed in version 10.0.7
- Splunk Enterprise 10.2.0 through 10.2.3 – Fixed in version 10.2.4
- Splunk Enterprise 10.4 – Not affected
It is also confirmed that Splunk Cloud customers are not impacted, as the cloud service does not use PostgreSQL sidecars.
Security researchers from watchTowr Labs recently published technical details showing how attackers could exploit the vulnerability to gain pre-authentication remote code execution.
The attack targets two PostgreSQL recovery endpoints:
/v1/postgres/recovery/backup/v1/postgres/recovery/restore
Researchers discovered that these endpoints could be abused to manipulate database backup and restoration processes. By carefully crafting database dumps and restoration requests, attackers can gain control over file-writing operations on the affected server.
The attack begins when a threat actor creates a malicious PostgreSQL database under their control. The attacker then tricks the vulnerable instance into connecting to that database and creating a backup file on the local system.
Next, the attacker uses the restore functionality to load the malicious database dump into the local PostgreSQL environment. During this process, a special configuration file known as .pgpass can be leveraged to authenticate as the PostgreSQL administrative user.
Once the malicious database is restored, attacker-controlled SQL commands are executed automatically by the PostgreSQL instance running on the Splunk server.
This gives attackers the ability to perform unauthorized actions within the database environment and potentially gain further access to the system.
Researchers explained that attackers can abuse PostgreSQL’s lo_export function, which is normally used to export binary data from a database and save it as a file on the operating system.
By leveraging this feature, threat actors can write files containing attacker-controlled content to arbitrary locations on the Splunk server.
This capability is particularly dangerous because it allows attackers to place malicious files directly on the system without requiring authentication or user interaction.
Security researchers noted that once they achieved control over the database restoration process, they were able to develop a method for writing arbitrary files to the local file system.
The arbitrary file write capability can be further weaponized to achieve full remote code execution.
Attackers can overwrite existing Python scripts that are regularly executed by Splunk services. One example highlighted by researchers is a Python script associated with Splunk Secure Gateway functionality.
By replacing or modifying such scripts with malicious code, attackers can ensure their payload is executed automatically by Splunk processes.
The attack chain generally follows these steps:
- Create a malicious PostgreSQL database controlled by the attacker.
- Configure the database to allow authentication and execution of specific PostgreSQL functions.
- Use the vulnerable backup endpoint to place a malicious database dump onto the Splunk file system.
- Trigger the restore endpoint to load the malicious database dump.
- Execute attacker-controlled SQL commands during the restoration process.
- Write malicious Python files to the Splunk server.
- Achieve remote code execution when the modified scripts are executed.
This sequence enables attackers to move from an unauthenticated network position to complete control over a vulnerable Splunk Enterprise server.
Although there are currently no public reports of active exploitation, the publication of detailed technical information significantly increases the risk of attacks.
Cybercriminals often move quickly once proof-of-concept details become publicly available. Security researchers and threat actors alike can analyze the published information and develop working exploits within a short period.
Organizations that delay patching may become attractive targets for opportunistic attackers scanning the internet for vulnerable Splunk deployments.
Because Splunk is widely used for security monitoring, log management, and threat detection, a successful compromise could have serious consequences. Attackers gaining control of a server may be able to access sensitive logs, manipulate security data, disrupt monitoring capabilities, or establish a foothold for further attacks within the network.
Organizations using Splunk Enterprise should take the following steps immediately:
- Upgrade to Enterprise 10.0.7 or later if running the 10.0 branch.
- Upgrade to Enterprise 10.2.4 or later if running the 10.2 branch.
- Verify whether PostgreSQL sidecar services are exposed to untrusted networks.
- Review system logs for suspicious access to PostgreSQL recovery endpoints.
- Monitor Splunk infrastructure for unexpected file modifications and unusual activity.
- Apply security updates as part of an accelerated patch management process.
The discovery of CVE-2026-20253 highlights how authentication weaknesses in supporting services can create severe security risks. With a CVSS score of 9.8 and the potential for unauthenticated remote code execution, this vulnerability represents a major threat to organizations running affected versions of Splunk Enterprise.
While no active attacks have been reported so far, the release of detailed exploit information means defenders should act quickly. Updating vulnerable systems and reviewing network exposure are essential steps to reduce the risk of compromise and maintain the security of critical deployments.
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