CVE-2025-67124 is a vulnerability identified in svenstaro/miniserve version 0.32.0 that arises from a TOCTOU (time-of-check to time-of-use) race condition combined with a symbolic link (symlink) race during the upload finalization process when uploads are enabled. Miniserve is a lightweight static file server often used for quick file sharing. The vulnerability manifests when the server finalizes an upload by moving or renaming files in the upload destination directory. If an attacker has the capability to create or replace filesystem entries—such as files or symlinks—in the upload destination directory, they can exploit the race condition to cause the server to overwrite arbitrary files outside the intended upload or document root. This can lead to unauthorized modification or replacement of critical files on the host system. The attack scenario requires the attacker to have write access to the upload directory, which is common in deployments using shared writable directories or volumes, such as containerized environments or multi-tenant systems. There is no CVSS score assigned yet, and no public exploits have been reported. The vulnerability primarily threatens the integrity and availability of the system by enabling unauthorized file overwrites, which could lead to service disruption or privilege escalation if critical system files are overwritten. The lack of authentication requirements for the upload process in some configurations increases the risk. The vulnerability is particularly relevant for environments where miniserve is used in shared or multi-user contexts without strict filesystem permission controls. Since no patch links are currently available, mitigation relies on configuration changes and operational controls.

For European organizations, this vulnerability poses a significant risk especially in environments where miniserve is deployed with upload functionality enabled and shared writable directories are used. The ability to overwrite arbitrary files can lead to data integrity loss, service outages, or even system compromise if critical configuration or executable files are overwritten. Sectors such as cloud service providers, software development firms, and organizations using containerized or multi-tenant environments are particularly vulnerable. The impact extends to any system relying on miniserve for file sharing or distribution, potentially affecting internal tools or customer-facing services. Given the potential for unauthorized file modification without authentication, attackers could disrupt operations or implant malicious code. The absence of known exploits suggests the threat is currently theoretical but should be treated with urgency due to the ease of exploitation in permissive environments. European organizations with strict data protection and operational continuity requirements must prioritize mitigation to avoid reputational damage and compliance issues.

1. Immediately restrict write permissions on upload destination directories to trusted users only, eliminating shared writable volumes where possible. 2. Disable upload functionality in miniserve if not strictly required, reducing the attack surface. 3. Implement filesystem monitoring to detect unexpected file changes or symlink creations in upload directories. 4. Use container or OS-level access controls (e.g., AppArmor, SELinux) to limit miniserve's filesystem access scope. 5. Avoid running miniserve with elevated privileges; run it under a dedicated low-privilege user account. 6. Regularly audit deployment configurations to ensure no unauthorized write access exists. 7. Monitor official miniserve repositories and CVE databases for patches or updates addressing this vulnerability and apply them promptly. 8. Consider alternative file sharing solutions with more robust security controls if uploads are essential and shared writable directories cannot be avoided.