WinSCP TSCPFileSystem::SCPSink Arbitrary File Overwrite Vulnerability [CVE-2018-20684]
CVE Number – CVE-2018-20684
A vulnerability in the TSCPFileSystem::SCPSink function of WinSCP could allow an unauthenticated, remote attacker to overwrite arbitrary files on a targeted system.
The vulnerability is due to improper validation of user-supplied input related to the TSCPFileSystem::SCPSink function, as defined in the core/ScpFileSystem.cpp source code file of the affected software. An attacker could exploit this vulnerability by using an attacker-controlled Secure Copy Protocol (SCP) server to send an arbitrary file to a targeted system. An exploit could allow the attacker to overwrite arbitrary files on the system. If the attacker uses the recursive operation when sending the file to the system, the attacker could also manipulate subdirectories, which could be used to conduct further attacks.
WinSCP has confirmed the vulnerability and released software updates.
Analysis
- To exploit this vulnerability, an attacker may need to perform further reconnaissance on the targeted system to determine if the system could accept files from a remote host utilizing the affected application.
Safeguards
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Administrators are advised to apply the appropriate updates.
Administrators are advised to allow only trusted users to have network access.
Administrators are advised to run both firewall and antivirus applications to minimize the potential of inbound and outbound threats.
Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.
Administrators can help protect affected systems from external attacks by using a solid firewall strategy.
Administrators are advised to monitor affected systems.
Vendor Announcements
- WinSCP has released a bug report and a git commit at the following links: Bug 1675 and commit 49d876f2c5fc00bcedaa986a7cf6dedd6bf16f54
Fixed Software
- WinSCP has released software updates at the following link: WinSCP 5.14
Duncan is a technology professional with over 20 years experience of working in various IT roles. He has a interest in cyber security, and has a wide range of other skills in radio, electronics and telecommunications.