CVE-2018-8799 in rdesktop
Summary
by MITRE
rdesktop versions up to and including v1.8.3 contain an Out-Of-Bounds Read in function process_secondary_order() that results in a Denial of Service (segfault).
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Analysis
by VulDB Data Team • 07/06/2023
The vulnerability identified as CVE-2018-8799 affects rdesktop versions up to and including v1.8.3, presenting a critical out-of-bounds read condition within the process_secondary_order() function. This flaw manifests as a denial of service attack resulting in segmentation faults that crash the application. The rdesktop client is widely used for remote desktop protocol connectivity, particularly in enterprise environments where remote access to Windows systems is required. The vulnerability stems from inadequate input validation and bounds checking within the secondary order processing logic, which handles various graphical updates and user interaction elements during remote desktop sessions. When processing malformed or specially crafted secondary order data packets, the function fails to properly validate array indices or buffer boundaries, leading to memory access violations.
The technical implementation of this vulnerability occurs during the parsing of remote desktop protocol packets that contain secondary order information. The process_secondary_order() function receives data structures that define graphical operations such as bitmap updates, text rendering, or cursor positioning. Without proper bounds checking on array indices or packet length validation, the function attempts to read memory locations beyond the allocated buffer boundaries. This condition typically occurs when the remote desktop server sends malformed secondary order data that exceeds expected parameter limits or contains invalid array references. The flaw is particularly dangerous because it can be triggered through normal network communication without requiring authentication or special privileges, making it an attractive target for denial of service attacks.
From an operational impact perspective, this vulnerability creates significant risks for organizations relying on rdesktop for remote access capabilities. A successful exploitation results in immediate application termination, forcing users to reconnect to remote systems and potentially disrupting critical business processes. The segmentation fault behavior makes this particularly problematic in automated environments where rdesktop clients might be used in scripts or monitoring systems. Network administrators face challenges in preventing such attacks since they can originate from legitimate remote desktop servers or be injected through man-in-the-middle positions on the network. The vulnerability affects not only individual user sessions but can also impact large-scale deployments where multiple rdesktop instances are running simultaneously, potentially causing cascading failures in remote access infrastructure.
Security professionals should implement immediate mitigations including updating to rdesktop version 1.8.4 or later, which contains patches addressing the out-of-bounds read condition. Network segmentation and access controls should be enhanced to limit exposure of rdesktop clients to untrusted networks or remote systems. The vulnerability aligns with CWE-129, which addresses insufficient validation of length of input buffers, and demonstrates characteristics consistent with ATT&CK technique T1499.004 for network denial of service attacks. Organizations should also consider implementing intrusion detection systems that can identify malformed secondary order packets and monitor for unusual segmentation fault patterns in rdesktop processes. Additionally, network administrators should establish logging procedures that capture remote desktop protocol communications to identify potential exploitation attempts and maintain audit trails for forensic analysis. The patch for this vulnerability specifically addresses the missing bounds checking in the secondary order processing function, ensuring that all array accesses are validated against proper buffer boundaries before memory operations occur.