Earlier in 2025, a serious vulnerability labeled CVE-2025-22247 hit the security news cycle. It impacts the widely used VMware Tools, a staple for managing and enhancing virtual machine performance and usability. Though VMware platforms are renowned for their enterprise-grade security, this particular issue exposes how even small flaws in file handling code can turn into significant attack surfaces—especially when a malicious user is lurking inside the virtual machine (VM).

In this post, I’ll break down what CVE-2025-22247 is, how it works, and what an attacker could do, plus I’ll share technical examples and point you to more resources for responsible research. If you’re running VMware in your organization, you’ll want to read to the end.

Issue: Insecure file handling inside guest VMs

- Impact: Lets users with NO admin rights on a guest tamper local files leading to insecure file operations.

What’s the Vulnerability?

The vulnerability stems from insecure file operations performed by VMware Tools when interacting with local system files inside a VM. Essentially, VMware Tools executes certain operations (like log writes, config changes, or data sharing) inside the guest, but does so using file handling code that's unaware (or unprotected) against typical file attack vectors, like symlink attacks, race conditions, and privilege confusion.

A user inside the VM, even without admin rights, can force VMware Tools’ processes to interact with files in unintended or dangerous ways—possibly overwriting critical files, gaining sensitive information, or escalating their access.

How Does the Exploit Work?

Let’s get specific. Imagine VMware Tools on a Windows or Linux VM tries to write a status update to a file in the user's temp directory, e.g., /tmp/vmtools_status.log. If file ownership or symlink checks aren’t properly done, a local attacker can replace or redirect that file.

Classic Example: Time-of-check to time-of-use (TOCTOU) Race Condition

1. Attacker notices VMware Tools creates or writes /tmp/vmtools_status.log after a process check.
2. Attacker deletes or moves the original file and quickly places a symbolic link named /tmp/vmtools_status.log pointing to a sensitive file (/etc/shadow, for example).
3. When VMware Tools writes to the status file, it unknowingly writes to /etc/shadow, overwriting sensitive data.

On Windows, the principle is similar, but with NTFS reparse points or hard links.

# Remove any existing status file
rm -f /tmp/vmtools_status.log

# Create a symlink to /etc/shadow
ln -s /etc/shadow /tmp/vmtools_status.log

# Trigger VMware Tools operation that will write to the log
/bin/vmtoolsd --some-action-that-logs

# If vulnerable, /etc/shadow now contains log data or is corrupted!

> Warning: This is for educational/research purposes only. Do not test on production or unauthorized systems.

Real-World Attack Scenario

Attackers don’t need to fully “take over” a VM. If they already have a foothold (say, as a regular user or web shell), they simply wait for an admin or process to run VMware Tools operations, then swap out or redirect those files. This could:

Lead to further privilege escalation under specific circumstances

*This form of “living off the land” attack is hard to detect, as it uses legitimate system processes!*

Fixes & Mitigation

VMware has released updates for affected Tools versions. The patched Tools now verify file types, ownership, and permissions before writing, and avoid following symlinks/hardlinks where possible.

Upgrade Advice:
Update VMware Tools in all your guests as soon as possible from VMware’s official advisory. See also the official CVE entry:
- NIST National Vulnerability Database: CVE-2025-22247

Limit which users can log into VMs.

- Remove unnecessary users and restrict shell/remote access.

References

1. VMware Security Advisory: VMSA-2025-XXXX
2. NIST CVE Database: CVE-2025-22247
3. Symlink Race Attacks Explained (OWASP)
4. Responsible Use: VMware’s Policy

Final Thoughts

The lesson from CVE-2025-22247 is one security teams know but need to keep reminding themselves: never trust user-writable directories or files, even if you think you control the application! Virtualization “guest tools” often have elevated context, making their mistakes even more impactful for attackers.

Keep all your tools—including those that seem “background”—up to date. And remember, sometimes the simplest bugs can open the door to serious threats. Stay safe out there!


*This analysis is exclusive. Please link back if you find this helpful!*

Timeline

Published on: 05/12/2025 11:15:49 UTC
Last modified on: 05/14/2025 17:15:47 UTC