CVE-2025-11947 identifies a heap-based buffer overflow vulnerability in the bftpd FTP server, specifically within the expand_groups function located in the options.c file, which handles configuration file parsing. The vulnerability affects bftpd versions 6.0, 6.1, and 6.2. The flaw arises from improper handling of group expansion data, allowing an attacker with local access and limited privileges to manipulate input that leads to a heap overflow condition. This can potentially cause memory corruption, leading to application crashes or, in theory, arbitrary code execution. However, exploitation is considered highly complex due to the need for local access, the difficulty in crafting the exploit, and the requirement for precise manipulation of the configuration handler. The vendor has not responded to disclosure requests and no official patches have been released. Although a public exploit exists, no widespread exploitation has been observed in the wild. The vulnerability's CVSS 4.0 score is 2.0, reflecting low severity primarily because the attack vector is local, requires high complexity, and the impact on confidentiality, integrity, and availability is limited. The vulnerability does not require user interaction and the scope is limited to the local system running the vulnerable bftpd versions.

For European organizations, the direct impact of this vulnerability is limited due to the requirement for local access and the complexity of exploitation. However, organizations that use bftpd FTP servers in critical environments or as part of legacy systems could face risks of service disruption or potential privilege escalation if attackers gain local access. The heap overflow could lead to denial of service through crashes or, in worst cases, arbitrary code execution, which might compromise system integrity or confidentiality. Given the lack of vendor response and patches, organizations relying on bftpd must consider the risk of targeted attacks, especially in environments where local user accounts are less strictly controlled. The impact is more pronounced in sectors where FTP servers are integral to operations, such as manufacturing, research institutions, or government agencies in Europe. The low CVSS score suggests limited immediate risk but does not preclude exploitation in high-value targets with insider threat scenarios or compromised local accounts.

1. Restrict local access to systems running bftpd to trusted administrators only, enforcing strict access controls and monitoring local user activities. 2. Implement host-based intrusion detection systems (HIDS) to detect anomalous behavior or crashes related to bftpd processes. 3. Consider disabling or replacing bftpd with more actively maintained FTP server software that has no known vulnerabilities. 4. If continuing to use bftpd, conduct code audits or develop custom patches to address the heap overflow in the expand_groups function. 5. Employ application sandboxing or containerization to limit the impact of potential exploitation. 6. Regularly review and harden configuration files to minimize attack surface and avoid untrusted input in group expansion features. 7. Maintain comprehensive logging and alerting for local privilege escalations or unexpected process terminations. 8. Educate local users and administrators about the risks of local exploitation and enforce least privilege principles.