Attack Chain

1. Attacker identifies a target running a vulnerable version of Adminer (prior to 5.4.3) via banner grabbing or service discovery.
2. Attacker interacts with the Adminer login interface, targeting the server field input.
3. Attacker submits a crafted request containing a semicolon-delimited DSN string designed to inject ODBC configuration parameters.
4. The vulnerable PHP code processes the input and initializes a PDO connection using the malicious DSN string.
5. The underlying database driver (specifically MS SQL PDO) processes the injected 'TraceFile' and 'TraceOn' parameters.
6. The application writes the trace output, which includes the injected PHP payload, to a file in the web root.
7. The attacker sends an HTTP request to the newly created file, triggering the web server to execute the injected PHP code.
8. Successful execution of the payload provides the attacker with remote code execution (RCE) on the server.

Impact

Successful exploitation of this vulnerability allows unauthenticated attackers to achieve arbitrary remote code execution on the server hosting Adminer. This can lead to total system compromise, data exfiltration, lateral movement within the network, and the deployment of persistent malware or backdoors. Organizations across any sector using Adminer to manage database instances are susceptible to this risk if they are running version 5.4.3 or earlier.

Recommendation

• Update Adminer to version 5.4.3 or later immediately to mitigate CVE-2026-56705.
• Inspect web server logs for requests containing semicolons or common ODBC parameters like 'TraceFile' directed at the Adminer login endpoint.
• Implement access controls or network segmentation to restrict access to the Adminer interface to authorized personnel only.
• Deploy the Sigma rule below to monitor for exploitation attempts against the Adminer service.