CVE-2018-20177 in rdesktop
Summary
by MITRE
rdesktop versions up to and including v1.8.3 contain an Integer Overflow that leads to a Heap-Based Buffer Overflow in the function rdp_in_unistr() and results in memory corruption and possibly even a remote code execution.
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Analysis
by VulDB Data Team • 08/01/2023
The vulnerability identified as CVE-2018-20177 represents a critical security flaw affecting rdesktop versions up to and including v1.8.3, specifically within the rdp_in_unistr() function. This issue stems from an integer overflow condition that subsequently triggers a heap-based buffer overflow, creating a pathway for remote code execution. The vulnerability exists within the Remote Desktop Protocol implementation, where the software fails to properly validate input data lengths during Unicode string processing, leading to memory corruption that can be exploited by remote attackers.
The technical flaw manifests when the rdesktop client processes Unicode strings received from a remote RDP server. During this processing, an integer overflow occurs in the calculation of buffer sizes needed to store Unicode data, which then results in insufficient buffer allocation. When the application attempts to write data beyond the allocated heap buffer boundaries, it triggers a heap-based buffer overflow condition. This memory corruption can be leveraged by attackers to execute arbitrary code on the affected system, potentially allowing complete system compromise. The vulnerability is classified as a CWE-128 Integer Overflow or Wraparound, which directly maps to the underlying cause of the memory corruption issue.
The operational impact of CVE-2018-20177 extends beyond simple remote code execution to encompass broader security implications for organizations relying on rdesktop for remote desktop connections. Attackers exploiting this vulnerability can gain unauthorized access to systems, escalate privileges, and potentially establish persistent backdoors within network environments. The vulnerability affects both Windows and Unix-like systems that utilize rdesktop for remote desktop protocol connectivity, making it particularly concerning for enterprise environments where remote access is common. According to ATT&CK framework, this vulnerability maps to T1071.004 Application Layer Protocol: Remote Desktop Protocol, and T1059 Command and Scripting Interpreter, as exploitation typically involves establishing remote connections and executing malicious commands. The vulnerability can be exploited through RDP connections, making it particularly dangerous for organizations that expose RDP services to untrusted networks.
Mitigation strategies for CVE-2018-20177 should prioritize immediate patching of affected rdesktop installations to version 1.8.4 or later, which contains the necessary fixes for the integer overflow condition. Organizations should also implement network segmentation to limit RDP access to trusted networks and enforce strong authentication mechanisms including multi-factor authentication. Additional protective measures include disabling unnecessary RDP services, implementing strict firewall rules that restrict RDP traffic to specific IP addresses, and monitoring network traffic for suspicious RDP connection patterns. Security teams should also consider deploying intrusion detection systems that can identify exploitation attempts targeting this specific vulnerability. The remediation process should include comprehensive testing of patched systems to ensure that the vulnerability has been properly addressed without introducing regressions in functionality. System administrators should also conduct regular vulnerability assessments to identify other potential weaknesses in their remote access infrastructure that could be exploited in conjunction with this vulnerability.