CVE-2026-63771 in Adminer
Summary
by MITRE • 07/20/2026
Adminer before 5.4.3 contains a cookie injection vulnerability that allows attackers to manipulate cookie attributes by injecting arbitrary values through the unsanitized X-Forwarded-Prefix HTTP header used in Set-Cookie path attributes. Attackers can exploit a misconfigured reverse proxy to downgrade SameSite protection and enable cross-origin authenticated requests, bypassing cookie security controls.
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Analysis
by VulDB Data Team • 07/20/2026
This vulnerability affects Adminer versions prior to 5.4.3 and represents a critical cookie injection flaw that undermines fundamental web application security mechanisms. The issue stems from improper input sanitization within the application's handling of the X-Forwarded-Prefix HTTP header, which is commonly used in reverse proxy configurations to indicate the original path prefix before routing requests. When this header contains unsanitized user-controllable data, it gets directly incorporated into Set-Cookie path attributes without adequate validation or encoding, creating a direct injection vector for malicious cookie manipulation.
The technical exploitation of this vulnerability occurs through misconfigured reverse proxy environments where attackers can manipulate the X-Forwarded-Prefix header to inject malicious values into cookie attributes. This injection allows threat actors to modify the path attribute of session cookies and potentially downgrade the SameSite protection level from strict or lax to none, effectively nullifying cross-site request forgery protections. The vulnerability specifically targets the cookie security controls that prevent unauthorized cross-origin requests by ensuring that cookies are only sent in first-party contexts, making it particularly dangerous for authenticated web applications.
The operational impact of this vulnerability extends beyond simple session hijacking capabilities to enable sophisticated attack vectors that bypass modern browser security mechanisms. Attackers can leverage this weakness to perform cross-origin authenticated requests against the Adminer application, potentially gaining unauthorized access to administrative functions and sensitive database operations. The attack surface is further expanded when organizations use reverse proxies with improper header handling configurations, as the injection point becomes accessible through standard HTTP request manipulation techniques. This vulnerability directly relates to CWE-113, which addresses "Improper Neutralization of CRLF Sequences in HTTP Headers" and CWE-352, covering Cross-Site Request Forgery (CSRF) vulnerabilities.
Organizations can mitigate this vulnerability by upgrading to Adminer version 5.4.3 or later, which implements proper input sanitization and validation for the X-Forwarded-Prefix header. Additional defensive measures include implementing strict header validation policies at the reverse proxy level to prevent arbitrary user data from being passed through to application components, configuring proper SameSite cookie attributes, and ensuring that all cookie path attributes are properly validated before being set. The mitigation strategy should also incorporate monitoring for unusual cookie behavior patterns and regular security assessments of proxy configurations to identify potential injection points. This vulnerability aligns with ATT&CK technique T1566.002 which covers "Phishing: Spearphishing Attachment" and T1071.004 which addresses "Application Layer Protocol: DNS," as attackers may use this weakness in conjunction with other techniques to establish persistent access to administrative interfaces.
The broader implications of this vulnerability highlight the importance of proper input validation across all application layers, particularly when dealing with headers that originate from external systems like reverse proxies. Security practitioners should consider implementing comprehensive header sanitization policies and regularly audit their proxy configurations to prevent similar injection vulnerabilities in other applications. This case demonstrates how seemingly innocuous configuration elements can create significant security weaknesses when not properly validated, emphasizing the need for defense-in-depth approaches to web application security that consider both application-level and infrastructure-level controls.