CVE-2020-11045 in FreeRDP
Summary
by MITRE
In FreeRDP after 1.0 and before 2.0.0, there is an out-of-bound read in in update_read_bitmap_data that allows client memory to be read to an image buffer. The result displayed on screen as colour.
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Analysis
by VulDB Data Team • 10/15/2020
The vulnerability identified as CVE-2020-11045 represents a critical out-of-bounds memory read flaw within the FreeRDP remote desktop protocol implementation. This issue affects versions of FreeRDP between 1.0 and 2.0.0, creating a significant security risk for remote desktop connections that utilize this software stack. The flaw manifests specifically within the update_read_bitmap_data function, which processes bitmap data during remote desktop sessions. This function fails to properly validate input boundaries when reading bitmap information from client connections, leading to unauthorized memory access patterns.
The technical implementation of this vulnerability stems from inadequate bounds checking within the bitmap data processing pipeline. When a remote client sends bitmap data to a FreeRDP server, the update_read_bitmap_data function does not sufficiently validate the size parameters or memory offsets associated with the incoming data. This allows an attacker to craft malicious bitmap data that references memory locations beyond the intended buffer boundaries. The vulnerability operates at the protocol level where remote desktop clients communicate with servers, making it particularly dangerous in networked environments where untrusted clients might connect to vulnerable FreeRDP implementations. The flaw aligns with CWE-129, which addresses insufficient validation of length of input buffers, and represents a classic example of improper input validation leading to memory corruption vulnerabilities.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can potentially enable attackers to extract sensitive data from the server's memory space. When the out-of-bounds read occurs, the system may inadvertently expose portions of memory containing confidential information, session data, or cryptographic keys that could be displayed as color artifacts on the screen. This behavior creates a potential information leakage vector that could be exploited by malicious actors to reconstruct sensitive data from memory dumps or to gain insights into the target system's internal state. The vulnerability particularly affects environments where FreeRDP serves as a remote desktop gateway or where it handles connections from untrusted external clients. According to ATT&CK framework, this vulnerability maps to T1046 for network service scanning and T1005 for data from local system, as it allows for memory reconnaissance and information gathering from compromised systems.
Mitigation strategies for CVE-2020-11045 primarily involve upgrading to FreeRDP version 2.0.0 or later, where the out-of-bounds read vulnerability has been addressed through proper input validation and boundary checking mechanisms. Organizations should also implement network segmentation and access controls to limit exposure of FreeRDP services to untrusted networks. Additional defensive measures include monitoring for anomalous bitmap data patterns in network traffic and implementing intrusion detection systems that can identify potential exploitation attempts. The vulnerability demonstrates the importance of proper memory management practices in protocol implementations and serves as a reminder of the critical need for thorough input validation in network services handling user-provided data. Security teams should also consider implementing application-level firewalls and network access control lists to restrict access to FreeRDP services and reduce the attack surface for this and similar vulnerabilities.