CVE-2025-34075 is a vulnerability in HashiCorp Vagrant involving incorrect default permissions that enable a virtual machine (VM) escape attack. Vagrant automatically mounts the host system's project directory into the guest VM using a synced folder, typically at /vagrant on Linux/macOS or C:\vagrant on Windows. This mount includes the Vagrantfile, a Ruby script that Vagrant evaluates on the host whenever a vagrant command is executed. The vulnerability arises because the guest VM has write access to this mounted directory, allowing a low-privileged attacker who gains shell access inside the guest VM to append arbitrary Ruby code to the Vagrantfile. When the host user subsequently runs any vagrant command in that project directory, the malicious Ruby code executes on the host with the privileges of the host user running Vagrant. This creates a guest-to-host code execution vector, effectively enabling VM escape in multi-tenant or adversarial environments where the guest VM is compromised. The vulnerability is rooted in CWE-276 (Incorrect Default Permissions), CWE-668 (Exposure of Resource to Wrong Sphere), and CWE-94 (Improper Control of Generation of Code). The CVSS 4.0 base score is 5.4 (medium severity), reflecting the requirement for authenticated access to the guest VM, user interaction on the host, and the local attack vector, but with high impact on confidentiality, integrity, and availability due to host code execution. No known exploits are currently reported in the wild, and no patches have been linked yet. This vulnerability highlights a design oversight in Vagrant’s default synced folder behavior, where guest-writable host configuration files are executed without sufficient security controls or warnings about the risks of guest modification.

For European organizations using Vagrant for development, testing, or deployment automation, this vulnerability poses a significant risk especially in environments where multiple users or tenants share VMs or where untrusted code runs inside guest VMs. An attacker who compromises a guest VM with low privileges can escalate to execute arbitrary code on the host machine, potentially leading to full host compromise. This can result in data breaches, unauthorized access to sensitive information, disruption of development workflows, and lateral movement within corporate networks. Organizations relying on Vagrant in regulated industries such as finance, healthcare, or critical infrastructure may face compliance violations if this vulnerability is exploited. The risk is heightened in scenarios where the host user has elevated privileges or access to sensitive resources. Additionally, the requirement for user interaction on the host (running a vagrant command) means social engineering or insider threats could facilitate exploitation. The vulnerability undermines the isolation guarantees typically expected from VM environments, impacting trust in development and testing infrastructure.

To mitigate this vulnerability, European organizations should: 1) Immediately restrict write permissions on the synced folder, especially the Vagrantfile, from the guest VM side. This can be done by configuring Vagrant to use synced folder options that mount the directory as read-only for the guest or by using alternative synced folder mechanisms that do not allow guest write access to host configuration files. 2) Educate developers and users to avoid running vagrant commands in project directories if the guest VM is untrusted or potentially compromised. 3) Implement strict access controls and monitoring on guest VMs to prevent unauthorized shell access. 4) Use host-based intrusion detection and file integrity monitoring to detect unexpected modifications to the Vagrantfile. 5) Consider isolating Vagrant usage to dedicated, non-critical hosts or virtual machines that do not contain sensitive data or credentials. 6) Regularly update Vagrant and monitor for official patches addressing this vulnerability. 7) Employ multi-factor authentication and network segmentation to limit attacker movement from guest to host. 8) Review and harden the development environment security posture, including limiting user privileges on hosts running Vagrant.