CVE-2026-114470 in hMailServer
Summary
by MITRE • 10/22/2026
Cross-site request forgery in the REST API of Progressive Robot hMailServer 6.0.0 through 6.3.6 allows a remote attacker to make an authenticated user's browser perform a state-changing request. The REST API accepts HTTP Basic authentication and answers a browser with a Basic sign-in box; a browser caches the credential once the box is answered and sends it with later requests to that origin, including a top-level form post from another site, and the server reads a request body whatever its declared content type. The cross-site protection covered only the cookie session (a header a cross-site form cannot set, and a SameSite=Strict cookie); HTTP Basic was not held to it. A page under an attacker's control, visited by a user whose browser holds a cached Basic credential for the REST API - typically an administrator who signed in through the box - could therefore cause a state-changing request such as creating a domain, an account or an API key, or changing a setting, with the victim's credential. The attacker cannot read the cross-origin response, so the forgery is blind.
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Analysis
by VulDB Data Team • 10/22/2026
The vulnerability identified in hMailServer versions 6.0.0 through 6.3.6 represents a critical Cross-Site Request Forgery flaw within its REST API implementation. This security defect allows remote attackers to compel authenticated users, particularly those with administrative privileges, to perform unintended state-changing actions without their knowledge or consent. The core of the issue lies in how the server handles HTTP Basic authentication compared to cookie-based session management. While the application correctly implements SameSite=Strict cookies and validates them against cross-site requests, it fails to apply equivalent protections to credentials transmitted via the Authorization header using HTTP Basic Authentication. This inconsistency creates a significant gap in the defense-in-depth strategy employed by the software.
Technically, the vulnerability exploits the standard behavior of web browsers regarding cached authentication credentials. When an administrator accesses the hMailServer REST API and enters their username and password into the browser's native basic authentication dialog box, the browser caches these credentials for that specific origin. Subsequently, if this user visits a malicious webpage controlled by an attacker, that page can initiate a POST request to the hMailServer REST API endpoint. Because browsers automatically attach cached Basic Auth headers to requests made to the authenticated origin regardless of the requesting site's origin, the server receives what appears to be a legitimate, authorized request from the victim. Crucially, the hMailServer REST API is configured to accept and process request bodies based on their declared content type rather than strictly validating the source or context of the request headers in this specific authentication flow. This allows the attacker to submit payloads that create new domains, add user accounts, generate API keys, or modify critical server settings.
The operational impact of this vulnerability is severe due to the high privilege level typically associated with users who interact directly with administrative REST APIs. An successful exploitation could lead to unauthorized access through newly created admin accounts, persistence via generated API keys, or disruption of service by altering core configuration settings. Although the attack vector is blind—meaning the attacker cannot read the response from the server due to cross-origin resource sharing restrictions—the ability to execute arbitrary state-changing commands remains highly dangerous. The lack of visibility into the result does not mitigate the risk, as many administrative actions such as account creation or key generation have immediate and irreversible consequences for system security posture.
This flaw aligns with CWE-352, which describes Cross-Site Request Forgery (CSRF), specifically highlighting the failure to verify that a request was intentionally initiated by the user rather than forged by a third party. Furthermore, from an ATT&CK perspective, this technique corresponds to T1078, Valid Accounts, as it involves the misuse of legitimate credentials to gain unauthorized access or perform actions within the system. The vulnerability underscores the importance of treating all authentication mechanisms with equal rigor regarding origin validation and request integrity checks.
To mitigate this risk, administrators should immediately upgrade hMailServer to a version later than 6.3.6 where these protections have been addressed. In environments where upgrading is not immediately feasible, network-level controls such as restricting access to the REST API endpoints via IP whitelisting can reduce exposure. Additionally, implementing strict Content Security Policy headers and ensuring that all administrative interfaces require multi-factor authentication or explicit user interaction for sensitive operations can provide additional layers of defense against automated forgery attempts. Regular audits of active sessions and API key usage are also recommended to detect any unauthorized changes resulting from potential exploitation.