CVE-2026-85603 in Grav
Summary
by MITRE • 09/04/2026
Grav versions before 1.10.55 contain a path traversal vulnerability in the admin plugin's Save As action that fails to validate the language code parameter. An authenticated admin user with admin.pages.create permission can supply directory traversal sequences in the lang POST field to write arbitrary .md files outside the pages directory with attacker-controlled content.
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Analysis
by VulDB Data Team • 09/04/2026
The Grav content management system, prior to version 10.55, contains a critical path traversal vulnerability within its administrative plugin interface. This flaw specifically affects the Save As functionality, which is designed to allow administrators to duplicate or relocate page files by specifying target directories and language codes. The underlying technical defect stems from an insufficient validation of user-supplied input in the lang POST parameter. Instead of strictly enforcing expected alphanumeric formats for locale identifiers, the application fails to sanitize directory traversal sequences such as dot-dot-slash (../) embedded within this field. This lack of rigorous input validation allows an attacker to manipulate the file system path resolution logic during the save operation.
An authenticated administrator possessing admin.pages.create permissions can exploit this vulnerability by injecting carefully crafted directory traversal characters into the language code parameter when invoking the Save As action. By appending sequences like ../../../../etc/ or similar constructs, the attacker redirects the file write operation away from the intended pages directory structure. This capability enables the creation of arbitrary Markdown files in sensitive locations outside the designated content storage area. The attacker retains full control over the content written to these external paths, which can include malicious scripts, configuration overrides, or other payloads designed for further exploitation within the hosting environment.
The operational impact of this vulnerability is significant due to its potential to lead to remote code execution and unauthorized data manipulation. If Grav is deployed in a standard web server environment where uploaded files are executed as scripts (such as PHP), writing executable content into accessible directories can result in complete system compromise. Even if direct code execution is not immediately possible, the ability to write arbitrary files allows for defacement, integrity violation of critical configuration files, or planting backdoors that persist across updates. This represents a severe breach of confidentiality and integrity within the application's security model.
From an industry standards perspective, this vulnerability aligns with CWE-22: Improper Limitation of a Pathname to a Restricted Directory (Path Traversal). The failure occurs because the software does not properly neutralize special elements that could cause paths to transition outside of restricted directories or files. In terms of offensive security frameworks, this exploit maps to MITRE ATT&CK technique T1059: Command and Scripting Interpreter if used for code execution, or more broadly to Initial Access techniques involving web application exploits where the attacker leverages valid credentials to perform unauthorized actions that compromise system integrity.
Mitigation strategies should prioritize immediate upgrading of the Grav installation to version 10.55 or later, which addresses this input validation deficiency. For environments where an upgrade is not immediately feasible, administrators can implement a Web Application Firewall (WAF) rule set designed to detect and block HTTP POST requests containing directory traversal patterns in parameters associated with file operations. Additionally, enforcing strict least-privilege principles by limiting admin.pages.create permissions only to trusted users reduces the attack surface. Regular security audits of custom plugins and core code for similar input validation gaps are recommended to prevent recurrence of such path manipulation issues.