CVE-2018-20176 in rdesktop
Summary
by MITRE
rdesktop versions up to and including v1.8.3 contain several Out-Of- Bounds Reads in the file secure.c that result in a Denial of Service (segfault).
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Analysis
by VulDB Data Team • 08/01/2023
The vulnerability identified as CVE-2018-20176 affects rdesktop versions up to and including v1.8.3, specifically targeting out-of-bounds read conditions within the secure.c file. This issue represents a critical security flaw that can lead to system instability and denial of service conditions. The vulnerability stems from improper input validation and memory access handling within the remote desktop protocol implementation, creating opportunities for malicious actors to exploit the software's memory management routines.
The technical flaw manifests as multiple out-of-bounds read operations that occur during the processing of secure communication protocols within rdesktop's implementation. These memory access violations happen when the application attempts to read data beyond allocated memory boundaries, particularly in the secure channel handling code. The vulnerability is classified under CWE-129 as an insufficient input validation, where the software fails to properly validate the size and boundaries of incoming data before processing. The flaw occurs during the parsing of remote desktop protocol messages, where buffer overflows or underflows can occur when handling encrypted or compressed data streams.
The operational impact of this vulnerability is significant as it can result in immediate system crashes and segmentation faults, effectively causing a denial of service condition for legitimate users. When exploited, the vulnerability can cause rdesktop clients to terminate unexpectedly, disrupting remote desktop connections and potentially affecting business continuity. The segmentation fault conditions can also provide attackers with opportunities to perform further exploitation attempts or gather information about the target system's memory layout. From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1499.004 for network denial of service, where attackers can leverage memory corruption vulnerabilities to disrupt services.
Mitigation strategies for CVE-2018-20176 primarily involve immediate software updates to versions that have addressed the out-of-bounds read conditions. System administrators should prioritize patching affected rdesktop installations and ensure that all remote desktop services are updated to the latest stable releases. Additionally, implementing network-level protections such as firewall rules to restrict access to remote desktop ports can help limit exposure. Input validation measures should be strengthened to prevent malformed data from reaching vulnerable code paths, and regular security audits of remote desktop implementations should be conducted to identify similar vulnerabilities. The fix typically involves proper bounds checking and memory allocation validation within the secure.c file, ensuring that all data reads occur within legitimate memory boundaries.