CVE-2018-8786 in FreeRDP
Summary
by MITRE
FreeRDP prior to version 2.0.0-rc4 contains an Integer Truncation that leads to a Heap-Based Buffer Overflow in function update_read_bitmap_update() 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-2018-8786 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 truncation error within the update_read_bitmap_update() function, which serves as a core component in processing bitmap updates during remote desktop sessions. The flaw occurs when handling certain bitmap data structures, creating a scenario where integer overflow conditions lead to improper memory allocation calculations.
The technical execution of this vulnerability involves a specific sequence where integer values representing bitmap dimensions or data sizes are truncated during processing, causing the system to allocate insufficient memory for the actual data being processed. This integer truncation creates a heap-based buffer overflow condition that can be exploited by remote attackers to manipulate memory contents. The vulnerability specifically targets the heap memory management within FreeRDP's update processing subsystem, where bitmap data is handled during remote desktop sessions.
The operational impact of this vulnerability extends beyond simple memory corruption, potentially enabling remote code execution capabilities for attackers who can craft malicious bitmap data to trigger the overflow condition. When exploited successfully, this vulnerability allows attackers to execute arbitrary code on the target system with the privileges of the FreeRDP service process, which could lead to complete system compromise. The remote nature of the attack means that exploitation can occur without physical access to the target system, making it particularly dangerous in networked environments where remote desktop services are exposed to external networks.
This vulnerability aligns with CWE-190, which specifically addresses integer overflow and underflow conditions, and demonstrates how improper integer handling can lead to memory corruption vulnerabilities. From an attack perspective, this flaw maps to several ATT&CK techniques including T1059 for remote code execution and T1105 for command and control communications. The vulnerability's classification as a heap-based buffer overflow indicates that it operates within the heap memory management system, making it susceptible to exploitation through carefully crafted input data that manipulates heap metadata.
Organizations utilizing FreeRDP for remote desktop connections should prioritize immediate patching to version 2.0.0-rc4 or later, as this represents the first fixed release addressing the integer truncation issue. Additional mitigations include implementing network segmentation to limit exposure of FreeRDP services, deploying intrusion detection systems to monitor for suspicious bitmap data patterns, and applying input validation controls to restrict the size and format of bitmap data accepted by the service. The vulnerability highlights the importance of proper integer handling in security-critical applications and serves as a reminder of the potential consequences when mathematical operations do not properly account for overflow conditions in memory management scenarios.