CVE-2026-114475 in hMailServer
Summary
by MITRE • 10/21/2026
Missing authorization in the REST role-management routes of Progressive Robot hMailServer 6.3.4 through 6.3.6 allows a remote authenticated user whose credential is confined to named domains to modify a custom role that accounts in other domains hold, and to create custom roles and delete any that no account holds. The routes that create, update and delete a custom role require the manage_roles permission, which only the serveradmin role holds; but a full-scope API key issued for named domains, and serveradmin assigned with a domain list, are serveradmin confined to those domains and hold manage_roles. The server's authorization gate did not refuse the three role routes to a confined credential and the route named no domain, so a credential issued to one tenant could raise or lower the permissions of a custom role assigned across other tenants - granting another domain's role every permission over its mailboxes and settings, or removing what it needs. A custom role may not hold administer_server, administer_domain or manage_roles, so the confined credential cannot make itself or another a server administrator by creating or rewriting a custom role.
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Analysis
by VulDB Data Team • 10/21/2026
The vulnerability identified in Progressive Robot hMailServer versions 6.3.4 through 6.3.6 represents a critical failure in access control logic within the REST API's role management subsystem. This flaw allows an authenticated user, whose credentials are restricted to specific named domains, to perform administrative actions that should be reserved for global server administrators. Specifically, the vulnerability enables such users to modify custom roles assigned to accounts in other domains and to create or delete custom roles that are not currently held by any account. The root cause lies in a misconfiguration of authorization gates within the API routes responsible for creating, updating, and deleting custom roles. These routes require the manage_roles permission, which is ostensibly restricted to the serveradmin role. However, when a full-scope API key is issued with domain-specific restrictions, or when a user holds the serveradmin role but is confined to a specific list of domains, the system incorrectly grants them access to these sensitive endpoints without validating whether their actions impact resources outside their authorized scope.
From a technical perspective, this issue stems from an incomplete implementation of multi-tenancy isolation within the application's authorization layer. The API endpoint logic fails to verify that the target resource being modified or deleted belongs exclusively to domains permitted by the caller's credentials. Consequently, a credential issued for one tenant can inadvertently raise or lower the permissions of a custom role assigned across other tenants. This lack of boundary enforcement means that an attacker confined to Domain A could alter the permission set of a role used in Domain B. Such alterations could grant users from Domain B every available permission over their mailboxes and settings, effectively escalating privileges beyond what was intended by the system administrator. Conversely, it could also remove necessary permissions, leading to service disruption for legitimate users in those other domains.
The operational impact of this vulnerability is severe due to its potential for privilege escalation and data integrity compromise within a multi-tenant environment. Although the vulnerability description notes that custom roles cannot hold administer_server or manage_roles permissions, preventing an attacker from directly becoming a global server administrator through role manipulation, the ability to alter cross-domain roles remains dangerous. An attacker could grant excessive privileges to accounts in other domains, potentially leading to unauthorized access to sensitive email data across organizational boundaries. Alternatively, by removing critical permissions from shared roles, an attacker could cause denial of service for legitimate users who rely on those specific permission sets to function correctly. This undermines the fundamental security principle of least privilege and breaks the isolation guarantees expected in hosted mail server environments.
In terms of industry standard classifications, this vulnerability aligns with CWE-269 Improper Privilege Management, as it involves a user obtaining privileges they are not authorized to have within the context of other domains. It also relates to CWE-862 Missing Authorization, where access control checks fail to enforce restrictions on specific resources based on user identity or role scope. From an ATT&CK perspective, this behavior is consistent with T1078 Valid Accounts and potentially T1098 Authorized Impersonation if the attacker leverages the altered roles to assume higher privileges within other domains. The vulnerability highlights a common pitfall in REST API design where global administrative endpoints are exposed without sufficient scoping checks for multi-tenant applications.
Mitigation strategies must focus on enforcing strict resource-level authorization checks at the application layer. Developers should ensure that any endpoint modifying role definitions validates not only the user's permission to manage roles but also verifies that all resources affected by the operation fall within the domains authorized for that specific user or API key. Implementing a whitelist approach where domain-specific users are explicitly denied access to global configuration endpoints is essential. Additionally, applying principle of least privilege during the design phase can prevent such logical flaws from occurring in future releases. For organizations currently running vulnerable versions, immediate patching to version 6.3.7 or later is recommended. Until patched, administrators should restrict API key scopes strictly and monitor logs for unusual role modification activities originating from domain-confined accounts.