CVE-2025-48985 is a security vulnerability identified in the Vercel AI SDK, a software development kit used to integrate AI functionalities into applications hosted on Vercel's platform. The vulnerability specifically involves an input validation bypass that allows attackers to circumvent filetype whitelisting mechanisms during file uploads. This means that malicious actors could upload files with disallowed or potentially harmful extensions by exploiting the flaw in the SDK's validation logic. The affected versions include 5.0.51 and 5.1.0-beta.8, with patches released in versions 5.0.52, 5.1.0-beta.9, and 6.0.0-beta. The vulnerability is categorized under CWE-20 (Improper Input Validation), indicating that the SDK did not sufficiently verify or restrict input data before processing it. According to the CVSS v3.1 scoring, the vulnerability has a score of 3.7 (low severity), with an attack vector of network (AV:N), high attack complexity (AC:H), no privileges required (PR:N), no user interaction (UI:N), unchanged scope (S:U), no confidentiality impact (C:N), low integrity impact (I:L), and no availability impact (A:N). This suggests that while exploitation is possible remotely without authentication or user interaction, the complexity of the attack is high, and the impact is limited to integrity, such as unauthorized file uploads that could potentially modify or inject malicious content. No known exploits have been reported in the wild, indicating that the threat is currently theoretical but should be addressed proactively. The vulnerability primarily affects applications that rely on the Vercel AI SDK for file upload functionalities, potentially exposing them to risks such as uploading malicious scripts or unauthorized files that could be used for further attacks or data manipulation.

For European organizations, the impact of CVE-2025-48985 is primarily related to the integrity of applications using the vulnerable Vercel AI SDK versions. Attackers could bypass filetype restrictions and upload unauthorized files, potentially leading to injection of malicious content or unauthorized modifications. While the vulnerability does not directly compromise confidentiality or availability, the integrity breach could facilitate secondary attacks such as webshell deployment, malware hosting, or defacement. Organizations relying on Vercel’s AI SDK for critical or customer-facing applications may face reputational damage and operational disruptions if exploited. Given the low CVSS score and high attack complexity, widespread exploitation is unlikely, but targeted attacks against high-value assets remain a concern. European entities with stringent compliance requirements around data integrity and software supply chain security should prioritize remediation to avoid regulatory penalties and maintain trust.

The primary mitigation is to upgrade the Vercel AI SDK to versions 5.0.52, 5.1.0-beta.9, or 6.0.0-beta where the vulnerability is fixed. Organizations should audit their software dependencies to identify usage of affected SDK versions and enforce timely patching. Additionally, implement strict server-side validation of uploaded files beyond client-side checks, including MIME type verification, file signature validation, and content scanning for malware. Employ application-layer firewalls or web application firewalls (WAFs) to detect and block suspicious file uploads. Restrict file upload permissions and storage locations to minimize potential damage from unauthorized files. Conduct regular security assessments and penetration testing focused on file upload functionalities. Finally, monitor logs and alerts for unusual upload activities and establish incident response procedures to quickly address any exploitation attempts.