CVE-2026-56706 in Adminer
Summary
by MITRE • 08/25/2026
Adminer before 5.4.3 uses a CSRF token scheme that transmits both the XOR mask and the masked value in every token (format (rand XOR secret):rand), allowing anyone who observes a single CSRF token (e.g., via network sniffing, log files, Referrer header, or XSS) to recover the session secret with a single XOR operation and forge unlimited valid tokens. The implementation is further weakened by a low-entropy session token (rand(1,1e6), ~20 bits) that permits blind brute-force, and by use of loose comparison (==) in token verification, enabling PHP type juggling. Exploitation enables cross-site request forgery against authenticated sessions, including execution of arbitrary SQL queries.
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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 failure in the implementation of Cross-Site Request Forgery protections, fundamentally undermining the integrity of administrative actions within the database management interface. The core technical flaw lies in the design of the CSRF token generation mechanism, which employs an XOR-based scheme that transmits both the random mask and the masked value together in every generated token. Specifically, the format follows a pattern where a secret key is XORed with a random integer to produce the transmitted payload alongside the original random integer itself. This architectural decision creates a direct mathematical pathway for attackers to reverse-engineer the session secret. By observing just a single valid CSRF token through common attack vectors such as network sniffing on unencrypted connections, log file analysis, or via Referrer header leakage and Cross-Site Scripting vulnerabilities, an adversary can perform a simple XOR operation between the mask and the masked value to immediately recover the underlying session secret. Once this secret is obtained, the attacker gains the ability to forge unlimited valid CSRF tokens, effectively bypassing all server-side validation checks designed to prevent unauthorized state-changing requests.
Beyond the cryptographic weakness in token generation, the implementation suffers from additional compounding vulnerabilities that significantly lower the barrier for exploitation. The random number generator used to create the initial entropy component relies on a low-entropy range defined by rand(1, 1e6), which provides approximately only twenty bits of randomness. This limited entropy space makes the tokens susceptible to blind brute-force attacks, allowing an attacker to guess valid tokens without necessarily needing to observe them first if they can interact with the application sufficiently. Furthermore, the token verification logic utilizes PHP loose comparison operators rather than strict equality checks. This introduces a risk of type juggling vulnerabilities where specific input strings could be coerced into matching numeric values during validation, potentially allowing forged or malformed tokens to pass authentication checks even without knowing the secret key. These combined weaknesses transform what should have been a robust defense-in-depth measure into a trivially bypassable control.
The operational impact of this vulnerability is severe, as it enables full cross-site request forgery against authenticated sessions with administrative privileges. An attacker can craft malicious web pages or scripts that trick an administrator into performing unintended actions while their session remains active in the browser. Because Adminer provides direct access to database management functions, successful exploitation allows for the execution of arbitrary SQL queries on behalf of the victim user. This capability extends far beyond simple account takeover; it permits data exfiltration, modification of critical application records, deletion of databases, and potentially further compromise of the underlying server infrastructure depending on the privileges granted to the Adminer instance. The ability to forge unlimited tokens means that once a single token is compromised or brute-forced, the attacker maintains persistent access to these destructive capabilities until the session expires or the secret key is rotated.
To mitigate this vulnerability, organizations must immediately upgrade Adminer to version 5.4.3 or later where the CSRF implementation has been revised to use cryptographically secure random number generators and proper token verification methods that avoid loose comparisons. In environments where upgrading is not immediately feasible, strict access controls should be enforced to limit who can access the Adminer interface, preferably restricting it to trusted IP addresses only. Additionally ensuring all administrative traffic occurs over HTTPS prevents network sniffing attacks from capturing tokens in transit. Implementing Content Security Policy headers can help mitigate Referrer header leakage and reduce the risk of XSS vectors that might expose token data. Regular rotation of session secrets and monitoring for unusual database query patterns can also aid in detecting potential exploitation attempts before significant damage is incurred. This incident highlights the importance of relying on established cryptographic libraries rather than custom XOR-based implementations for security-critical tokens, aligning with industry standards such as CWE-352 regarding Cross-Site Request Forgery and ATT&CK techniques related to credential access and lateral movement through database manipulation.