CVE-2026-56705 in Adminer
Summary
by MITRE • 08/25/2026
Adminer before 5.4.3 fails to sanitize the server field before constructing a PDO DSN string, allowing unauthenticated attackers to inject ODBC parameters via semicolons. Attackers can inject TraceFile and TraceOn parameters to write PHP code to the web root, achieving remote code execution when the trace file is accessed.
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Analysis
by VulDB Data Team • 08/25/2026
The vulnerability identified in Adminer versions prior to 5.4.3 represents a critical server-side request forgery and injection flaw rooted in improper input validation within the database connection handling logic. Specifically, the application fails to adequately sanitize the server field provided by the user before it is incorporated into the PHP Data Objects (PDO) data source name string. This lack of sanitization creates an avenue for unauthenticated attackers to manipulate the underlying configuration parameters that dictate how the PDO extension interacts with the target database system. By exploiting this weakness, an attacker can inject arbitrary ODBC connection parameters by utilizing semicolons as delimiters within the server input field. The core technical failure lies in the assumption that the server parameter is strictly a hostname or IP address, ignoring the possibility of it containing additional key-value pairs separated by standard connection string syntax characters.
This injection capability allows for sophisticated attacks beyond simple database enumeration or unauthorized access. Because PDO supports various driver-specific parameters, an attacker can inject specific ODBC options such as TraceFile and TraceOn. When these parameters are successfully injected into the DSN construction process, they instruct the underlying ODBC driver to enable tracing functionality and direct that trace output to a file path specified by the attacker. If the web server has write permissions for the document root directory or other accessible locations, an attacker can specify a PHP script filename as the target for this trace log. Consequently, every database interaction initiated through Adminer will result in data being written to this crafted file. Since ODBC tracing often includes raw SQL queries and potentially sensitive execution details, careful crafting of these inputs allows the injection of valid PHP code into the resulting file.
The operational impact of this vulnerability is severe, culminating in remote code execution on the target server. Once the malicious content is successfully written to a location within the web root via the trace log mechanism, an attacker can trigger its execution by simply requesting that specific URL through their browser or another HTTP client. This effectively grants the attacker full control over the application environment under the context of the web server process. The ability to execute arbitrary code bypasses traditional authentication mechanisms entirely, as this flaw is exploitable without valid credentials. It compromises the confidentiality, integrity, and availability of the system by allowing data exfiltration, further lateral movement within the network, or complete compromise of the hosting infrastructure.
From a classification perspective, this vulnerability aligns with CWE-94 Improper Control of Generation of Code (Code Injection) due to the injection of executable code via manipulated input parameters. It also relates closely to CWE-20 Improvement in Input Validation and CWE-78 Improper Neutralization of Special Elements used in an OS Command or Program, specifically within the context of application-level configuration strings rather than direct shell commands. In terms of adversary tactics, this exploit maps to MITRE ATT&CK technique T1190 Exploit Public-Facing Application, where attackers leverage vulnerabilities in internet-facing software to gain initial access. The specific method of writing files via trace logs can also be associated with T1562 Impair Defenses or T1059 Command and Scripting Interpreter if the executed code performs further actions on the host system.
Mitigation strategies for this vulnerability are straightforward but require immediate action from administrators and developers. The primary remediation is to upgrade Adminer to version 5.4.3 or later, where the server field sanitization has been corrected to prevent parameter injection via semicolons. For environments where an immediate upgrade is not feasible, temporary mitigations should focus on restricting access to the Adminer interface through network-level controls such as firewalls or IP whitelisting, ensuring that only trusted administrators can reach the login page. Additionally, enforcing strict file permission policies so that the web server process does not have write access to directories containing executable scripts can limit the impact of any successful code injection attempt. Regular security audits and input validation reviews are essential to prevent similar flaws in custom or third-party applications that handle dynamic configuration parameters.