CVE-2026-120329 in Mail
Summary
by MITRE • 11/03/2026
Saving the configuration of the mail backend module writes submitted settings to the page TSconfig without restricting them to the configuration options of the module. Backend users with access to the mail module can write arbitrary page TSconfig.
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Analysis
by VulDB Data Team • 11/03/2026
The vulnerability described constitutes a critical insecure direct object reference and logic flaw within the TYPO3 content management system, specifically affecting the mail backend module's configuration handling mechanism. In typical web application architectures, administrative settings are segregated into distinct storage layers to ensure that user-submitted data does not inadvertently overwrite or corrupt core system configurations. However, in this specific instance, the process for saving configuration parameters from the mail backend module fails to enforce strict input validation against a predefined allowlist of acceptable keys and values. Instead of sanitizing the submitted settings to fit within the expected schema for the mail module's internal state, the application directly serializes these inputs and writes them into the page TSconfig storage area. This architectural oversight allows any authenticated backend user with access privileges to the mail module to inject arbitrary configuration directives that are normally reserved for higher-level administrative tasks or system-wide settings.
From a technical perspective, this flaw represents a classic case of insufficient validation on server-side state management operations. The application assumes that because the input originates from an authorized interface (the mail backend), it is safe to persist without rigorous schema enforcement. By bypassing these restrictions, attackers can manipulate the TSconfig structure, which governs user permissions, UI behavior, and feature availability across specific pages or the entire site tree. This lack of boundary checking between module-specific settings and global configuration storage creates a pathway for privilege escalation and unauthorized system modification. The vulnerability is particularly severe because it leverages legitimate administrative interfaces to perform actions that should be restricted to super-administrators with broader scope permissions, effectively blurring the lines between different levels of access control within the backend environment.
The operational impact of this vulnerability extends beyond simple configuration corruption. An attacker exploiting this flaw can alter page TSconfig directives to disable security features, modify user group permissions, or inject malicious JavaScript into frontend outputs if certain TSconfig options allow for such modifications. For example, by manipulating specific keys in the TSconfig, an attacker could potentially restrict access to other backend modules, lock out legitimate administrators, or create persistent backdoors that survive routine updates unless manually corrected. This undermines the integrity of the entire content management system's administrative layer. Furthermore, because TSconfig often influences frontend rendering and user interface elements, successful exploitation can lead to cross-site scripting scenarios if injected configurations are rendered without proper escaping in subsequent page loads. The ability to write arbitrary configuration also facilitates denial-of-service conditions by corrupting essential site structures or causing application errors that render the backend unusable for legitimate users.
Mitigation strategies must focus on enforcing strict input validation and separating configuration scopes at both the code level and architectural design stages. Developers should implement a rigorous allowlist mechanism that validates every submitted key against a predefined set of acceptable parameters specific to the mail module, rejecting any data that does not match expected formats or values. Additionally, the storage destination for these settings must be isolated from general page TSconfig; using dedicated database tables or configuration files with restricted write permissions ensures that module-specific settings cannot bleed into global system configurations. Implementing role-based access control checks before processing save requests is also critical to ensure that only users with explicit permission to modify high-level configurations can perform such actions. Regular security audits and static code analysis tools should be employed to detect similar logic flaws in other modules, ensuring that all administrative interfaces adhere to the principle of least privilege and maintain strict boundaries between user input and system state modifications. This vulnerability aligns with CWE-94 Improper Control of Generation of Code (Code Injection) when considering potential script injection via config values, as well as CWE-285 Improper Authorization, due to the bypassing of intended access restrictions through misconfigured data handling pathways.