CVE-2020-10194 in Zimbra
Summary
by MITRE
cs/service/account/AutoCompleteGal.java in Zimbra zm-mailbox before 8.8.15.p8 allows authenticated users to request any GAL account. This differs from the intended behavior in which the domain of the authenticated user must match the domain of the galsync account in the request.
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Analysis
by VulDB Data Team • 04/18/2024
The vulnerability identified as CVE-2020-10194 resides within the Zimbra mailbox component, specifically in the AutoCompleteGal.java service handler located at cs/service/account/AutoCompleteGal.java. This issue affects Zimbra zm-mailbox versions prior to 8.8.15.p8 and represents a critical authorization bypass flaw that undermines the intended security boundaries of the system. The vulnerability manifests when authenticated users can request Global Address List (GAL) accounts without proper domain validation, effectively allowing cross-domain enumeration and access to user information that should be restricted to the authenticated user's own domain.
The technical flaw stems from insufficient input validation and authorization checks within the GAL auto-complete functionality. When an authenticated user makes a request to the AutoCompleteGal service, the system fails to verify that the requested GAL account belongs to the same domain as the authenticated user's account. This oversight creates a privilege escalation scenario where users can enumerate and access GAL entries from other domains within the same Zimbra deployment. The vulnerability operates at the application layer and specifically targets the directory service integration that facilitates GAL lookups, which is a fundamental component of email systems for user discovery and address completion.
The operational impact of this vulnerability extends beyond simple information disclosure to encompass potential reconnaissance activities and lateral movement opportunities within the email infrastructure. An attacker with valid credentials could systematically enumerate users across different domains, mapping the organizational structure and identifying potential targets for further attacks. This capability directly aligns with attack patterns described in the MITRE ATT&CK framework under the reconnaissance and credential access phases, where adversaries seek to understand the target environment and identify valuable user accounts. The vulnerability particularly affects organizations using Zimbra's galsync functionality, where multiple domains are synchronized and where proper domain isolation should be maintained.
Organizations affected by this vulnerability should immediately upgrade to Zimbra zm-mailbox version 8.8.15.p8 or later, which includes the necessary patches to enforce proper domain validation for GAL requests. Network segmentation and monitoring should be implemented to detect unusual patterns of GAL enumeration requests, particularly those that span multiple domains within the same deployment. Access controls should be reviewed to ensure that domain-specific restrictions are properly enforced, and regular security assessments should verify that authorization mechanisms function as intended. The vulnerability demonstrates the importance of proper input validation and domain boundary enforcement in multi-tenant email systems, aligning with CWE-284 which addresses improper access control in software systems. Organizations should also consider implementing rate limiting and anomaly detection for GAL lookup services to prevent automated enumeration attacks that could exploit this weakness.