CVE-2022-24883 in FreeRDP
Summary
by MITRE • 04/26/2022
FreeRDP is a free implementation of the Remote Desktop Protocol (RDP). Prior to version 2.7.0, server side authentication against a `SAM` file might be successful for invalid credentials if the server has configured an invalid `SAM` file path. FreeRDP based clients are not affected. RDP server implementations using FreeRDP to authenticate against a `SAM` file are affected. Version 2.7.0 contains a fix for this issue. As a workaround, use custom authentication via `HashCallback` and/or ensure the `SAM` database path configured is valid and the application has file handles left.
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Analysis
by VulDB Data Team • 05/05/2026
The vulnerability CVE-2022-24883 affects FreeRDP implementations that serve as RDP servers and authenticate users against SAM (Security Account Manager) files. This represents a critical authentication bypass flaw that allows unauthorized access when the server configuration contains an invalid SAM file path. The vulnerability specifically targets the server-side authentication mechanism where FreeRDP fails to properly validate the SAM file's existence and accessibility before attempting authentication operations. The flaw exists in versions prior to 2.7.0 and impacts systems that rely on FreeRDP for RDP server functionality with SAM-based authentication, creating a scenario where invalid credentials may be accepted due to the server's improper handling of missing or misconfigured SAM database files. This authentication weakness directly violates standard security principles and could enable attackers to gain unauthorized access to systems protected by RDP services.
The technical root cause of this vulnerability stems from inadequate input validation and error handling within the SAM file authentication process. When FreeRDP attempts to authenticate users against a SAM database, it does not properly verify that the specified file path actually points to a valid SAM file or that the application has proper read permissions. This results in the authentication system potentially accepting credentials even when the SAM database is inaccessible or non-existent, essentially creating a false positive authentication response. The flaw manifests when the system configuration specifies an invalid SAM file path, but the authentication routine continues processing without proper validation checks that would normally prevent such scenarios. This behavior aligns with CWE-20, which addresses improper input validation, and CWE-312, which covers exposure of sensitive information through improper error handling.
The operational impact of this vulnerability is significant for organizations relying on FreeRDP-based RDP servers with SAM authentication. Attackers could exploit this weakness to gain unauthorized access to systems without proper credentials, potentially leading to complete system compromise. The vulnerability particularly affects enterprise environments where RDP servers are configured for local authentication using SAM databases, making it a serious concern for network security. Organizations using FreeRDP versions before 2.7.0 could face unauthorized access to critical systems, data breaches, and potential lateral movement within their networks. The impact extends beyond simple credential guessing as this flaw allows authentication bypass regardless of the actual user credentials provided, making it particularly dangerous in environments with robust network segmentation.
Mitigation strategies for this vulnerability include immediate upgrade to FreeRDP version 2.7.0 or later, which contains the necessary patches to address the authentication bypass issue. Organizations should also implement the recommended workaround of configuring custom authentication through HashCallback mechanisms to avoid reliance on vulnerable SAM file authentication. Additionally, system administrators must ensure that all configured SAM database paths are valid and that applications have proper file handles and permissions to access these files. This aligns with ATT&CK technique T1078.002 which covers valid accounts through abuse of passwords and credential access, as the vulnerability essentially allows unauthorized access through malformed authentication configurations. Regular security audits should verify that all RDP server configurations properly validate authentication database paths and that access controls are appropriately enforced. The fix addresses the core authentication flow by implementing proper validation checks before proceeding with credential verification, thereby preventing the false positive authentication responses that characterized the vulnerable behavior.