CVE-2020-11522 in FreeRDP
Summary
by MITRE
libfreerdp/gdi/gdi.c in FreeRDP > 1.0 through 2.0.0-rc4 has an Out-of-bounds Read.
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Analysis
by VulDB Data Team • 05/19/2025
The vulnerability identified as CVE-2020-11522 affects the FreeRDP library, specifically within the gdi/gdi.c file, where an out-of-bounds read condition exists in versions greater than 1.0 through 2.0.0-rc4. This issue represents a critical security flaw that can potentially allow attackers to read memory locations beyond the intended bounds of allocated buffers. The vulnerability occurs during the processing of graphics data within the Remote Desktop Protocol implementation, making it particularly dangerous in remote desktop environments where FreeRDP is utilized. Such out-of-bounds read conditions often serve as entry points for more severe exploits, including memory corruption attacks that could lead to arbitrary code execution or information disclosure.
The technical flaw manifests when FreeRDP processes graphics operations through its GDI (Graphics Device Interface) subsystem, where insufficient bounds checking occurs on array indices or buffer access operations. This allows an attacker who can influence the graphics data stream to trigger memory access violations that may expose sensitive information from adjacent memory locations or potentially cause application crashes. The vulnerability falls under CWE-129, which specifically addresses insufficient validation of length of input buffers, and can be mapped to ATT&CK technique T1059.007 for execution through remote desktop protocols. The flaw is particularly concerning because it operates at the graphics processing layer where attackers can craft malicious graphics data to exploit the buffer overflow condition.
The operational impact of this vulnerability extends beyond simple memory corruption, as it can enable attackers to gain unauthorized access to sensitive data stored in memory, potentially including authentication credentials, session information, or other confidential data. In enterprise environments where FreeRDP is used for remote desktop connections, this vulnerability could be exploited to escalate privileges or establish persistent access to systems. The vulnerability affects any system running FreeRDP versions within the specified range, including those used for remote desktop gateway services, virtual desktop infrastructure implementations, and remote access solutions. Attackers could leverage this issue through crafted graphics data sent over RDP connections, making it particularly dangerous in networked environments where RDP is actively used.
Mitigation strategies for CVE-2020-11522 should prioritize immediate patching of affected FreeRDP installations to versions that have addressed the out-of-bounds read condition. Organizations should implement network segmentation to limit access to RDP services and deploy intrusion detection systems to monitor for suspicious graphics data patterns. Additional defensive measures include enabling network access controls, implementing multi-factor authentication for remote desktop access, and conducting regular security assessments of remote desktop configurations. Security teams should also consider monitoring for unusual memory access patterns or application crashes that might indicate exploitation attempts. The vulnerability demonstrates the importance of thorough input validation in graphics processing libraries and highlights the need for comprehensive security testing of remote desktop implementations. Organizations should also review their remote desktop security policies and ensure that only necessary RDP services are exposed to external networks, while maintaining up-to-date security patches across all systems that utilize FreeRDP components.