CVE-2026-2979 is a security vulnerability identified in FastApiAdmin, an administrative interface framework for FastAPI applications, affecting versions 2.0 through 2.2.0. The flaw resides in the user_avatar_upload_controller function within the Scheduled Task API component, located in the /backend/app/api/v1/module_system/user/controller.py file. This vulnerability allows an attacker to perform unrestricted file uploads remotely without requiring user interaction or elevated privileges beyond low-level access. The unrestricted upload means that the application does not properly validate or restrict the types, sizes, or contents of files uploaded via the avatar upload endpoint. Consequently, an attacker could upload malicious files such as web shells, scripts, or executables, potentially leading to remote code execution, privilege escalation, or persistent backdoors within the affected system. The vulnerability has been assigned a CVSS 4.0 base score of 5.3, indicating a medium severity level. The vector metrics indicate network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:L), no user interaction (UI:N), and low impact on confidentiality, integrity, and availability (VC:L, VI:L, VA:L). Although no confirmed exploits have been observed in the wild, a public exploit is available, increasing the risk of exploitation. The vulnerability affects organizations using FastApiAdmin for managing user avatars or administrative tasks, especially those exposing the API endpoint to untrusted networks. The lack of proper validation and access control in the upload function is the root cause, making it critical to implement strict file validation and access restrictions.

The unrestricted file upload vulnerability in FastApiAdmin can have significant impacts on organizations worldwide. Attackers exploiting this flaw can upload malicious files that may lead to remote code execution, allowing full system compromise. This can result in data breaches, unauthorized access to sensitive information, disruption of services, and potential lateral movement within the network. The vulnerability's ease of exploitation and remote attack vector increase the risk of widespread attacks, especially in environments where FastApiAdmin is exposed to the internet or untrusted networks. Organizations relying on FastApiAdmin for administrative interfaces or user management may face reputational damage, regulatory penalties, and operational downtime if exploited. The medium severity score reflects moderate impact, but the potential for escalation to critical outcomes exists if combined with other vulnerabilities or misconfigurations. The absence of authentication or user interaction requirements lowers the barrier for attackers, making it a viable target for automated attacks or exploitation by less skilled adversaries.

To mitigate CVE-2026-2979, organizations should immediately upgrade FastApiAdmin to a version where this vulnerability is patched once available. In the absence of an official patch, implement strict server-side validation of uploaded files, including checking file types, extensions, MIME types, and scanning for malicious content. Restrict upload permissions to authenticated and authorized users only, enforcing role-based access controls. Employ network-level protections such as web application firewalls (WAFs) to detect and block suspicious upload attempts. Isolate the upload directory from executable permissions to prevent execution of uploaded files. Monitor logs for unusual upload activity and conduct regular security audits of the affected API endpoints. Additionally, consider implementing content security policies and endpoint rate limiting to reduce attack surface. Educate developers and administrators about secure file handling practices and ensure secure coding standards are followed in future development. Finally, maintain an incident response plan to quickly address any exploitation attempts.