CVE-2018-8787 in FreeRDP
Summary
by MITRE
FreeRDP prior to version 2.0.0-rc4 contains an Integer Overflow that leads to a Heap-Based Buffer Overflow in function gdi_Bitmap_Decompress() and results in a memory corruption and probably even a remote code execution.
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Analysis
by VulDB Data Team • 06/12/2023
The vulnerability identified as CVE-2018-8787 represents a critical security flaw in the FreeRDP remote desktop protocol implementation that affects versions prior to 2.0.0-rc4. This issue manifests as an integer overflow condition that ultimately results in a heap-based buffer overflow within the gdi_Bitmap_Decompress() function, creating a significant attack surface for remote code execution. The flaw exists in the handling of bitmap decompression operations within the graphics device interface component of the remote desktop client, making it particularly dangerous for environments where remote desktop connections are frequently used.
The technical exploitation of this vulnerability occurs when a malicious remote desktop server sends specially crafted bitmap data to a vulnerable FreeRDP client. The integer overflow condition in the decompression logic causes an incorrect calculation of buffer sizes, leading to insufficient memory allocation for the decompressed bitmap data. When the decompression process attempts to write beyond the allocated heap buffer, it triggers a heap-based buffer overflow that can be leveraged by attackers to overwrite adjacent memory regions. This memory corruption can be manipulated to redirect program execution flow and potentially achieve remote code execution on the targeted system.
From an operational perspective, this vulnerability poses a severe risk to enterprise environments that rely on remote desktop protocols for administrative access, employee connectivity, or server management. The attack vector is particularly concerning because it can be executed remotely without requiring authentication, making it an attractive target for automated exploitation campaigns. The vulnerability affects both Windows and Linux systems running vulnerable FreeRDP versions, creating a broad attack surface across different operating environments. Network administrators and security teams must consider this flaw in their threat modeling exercises, particularly in environments where remote desktop services are exposed to untrusted networks or internet-facing systems.
The vulnerability maps to CWE-190, Integer Overflow or Wraparound, and CWE-121, Stack-based Buffer Overflow, while also aligning with ATT&CK technique T1210, Exploitation of Remote Services, and T1059, Command and Scripting Interpreter. The integer overflow in the bitmap decompression function demonstrates a classic software security flaw where inadequate input validation leads to memory corruption. Security professionals should implement immediate mitigations including patching to FreeRDP version 2.0.0-rc4 or later, implementing network segmentation to limit exposure of remote desktop services, and monitoring for suspicious connection attempts. Additionally, organizations should consider implementing network-level protections such as firewall rules that restrict access to remote desktop ports and deploy intrusion detection systems to identify potential exploitation attempts. The remediation process must include thorough testing of patched environments to ensure that the vulnerability is fully resolved without introducing compatibility issues with existing remote desktop workflows.