CVE-2020-6162 in bftpd
Summary
by MITRE
An issue was discovered in Bftpd 5.3. Under certain circumstances, an out-of-bounds read is triggered due to an uninitialized value. The daemon crashes at startup in the hidegroups_init function in dirlist.c.
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Analysis
by VulDB Data Team • 01/11/2020
The vulnerability identified as CVE-2020-6162 affects Bftpd version 5.3, a widely used FTP server implementation that has been deployed in various network environments for file transfer operations. This issue represents a critical security flaw that can compromise the availability and stability of the affected system. The vulnerability manifests as an out-of-bounds read condition that occurs during the daemon's startup process, specifically within the hidegroups_init function located in the dirlist.c source file. The improper handling of uninitialized memory values creates a scenario where the program attempts to access memory locations beyond the allocated bounds, leading to unpredictable behavior and system instability.
The technical root cause of this vulnerability stems from inadequate memory initialization practices within the hidegroups_init function, which is responsible for managing group visibility configurations in the FTP directory listing functionality. When the Bftpd daemon initializes and processes group-related configurations, it fails to properly initialize certain variables before use, resulting in the consumption of uninitialized memory values. This uninitialized data, when processed by the out-of-bounds read operation, causes the program to access memory locations that contain arbitrary data from the system's memory space. The vulnerability is particularly concerning because it occurs during the daemon's startup phase, meaning that any attempt to launch the service will trigger the crash, effectively rendering the FTP service unavailable.
From an operational perspective, this vulnerability presents a significant threat to system availability and can be exploited by malicious actors to perform denial-of-service attacks against FTP services. The crash occurs at startup, which means that legitimate users attempting to access the FTP service will encounter immediate service failures. The impact extends beyond simple service disruption as the vulnerability can be leveraged by attackers to systematically prevent FTP service availability, particularly in environments where the service is critical for file transfer operations. This vulnerability aligns with CWE-457, which describes the use of uninitialized variables, and can be classified under the broader category of memory safety issues that affect software reliability and security.
The exploitation of this vulnerability can be categorized under the ATT&CK technique T1499.004, which involves network denial of service attacks. Attackers can leverage this flaw to repeatedly attempt to start the Bftpd daemon, causing repeated crashes and system instability. The vulnerability also demonstrates characteristics of T1566.001, which involves social engineering through spearphishing with links, as attackers might create malicious FTP configurations or exploit other related vulnerabilities to trigger the out-of-bounds read condition. Security professionals should consider this vulnerability as part of a broader threat landscape where service availability is targeted, particularly in environments where FTP services are critical infrastructure components.
Organizations should implement immediate mitigation strategies including updating to patched versions of Bftpd that address the uninitialized variable handling in the hidegroups_init function. Additionally, system administrators should consider implementing monitoring solutions that can detect repeated startup failures and alert on potential exploitation attempts. The vulnerability highlights the importance of proper memory management practices and the need for comprehensive code review processes that specifically examine variable initialization and memory access patterns. Regular security assessments should include verification of uninitialized variable usage and proper bounds checking to prevent similar vulnerabilities from being introduced into software deployments. The incident underscores the critical need for adherence to secure coding practices and the implementation of automated code analysis tools that can identify such memory safety issues before they can be exploited in production environments.