CVE-2025-10585: What It Is and Why You Must Update Your Browser Now

Lucas Daniels
Sep 25
3 min read

What CVE-2025-10585 Is

Here’s what we know so far (as of mid-September 2025):

The vulnerability is a zero-day, meaning attacks are happening in the wild already.
It affects Google Chrome’s V8 JavaScript / WebAssembly engine. It’s a type confusion issue, which means the engine can mistake one kind of object for another. That can lead to memory corruption, crashes, or attackers executing arbitrary code on the victim’s machine.
Google’s Threat Analysis Group (TAG) discovered it on 16 September 2025 and has confirmed it’s being actively exploited.
The patched versions are: Chrome 140.0.7339.185/.186 for Windows and macOS, and 140.0.7339.185 for Linux.

In short: this is serious. If you’re using a version of Chrome older than the patched ones, you’re exposed.

Why It Matters for Small Businesses

Here are the key risks and implications:

Browsers are a front-line tool: your team uses Chrome for emails, dashboards, SaaS apps, and everything in between. A browser exploit can give attackers a stepping stone into internal systems.
Zero-days tend to bypass many standard defenses. Things like firewalls or anti-virus may not catch an exploit if it’s using a previously unknown flaw.
A compromised device (laptop, workstation) can lead to exposure of credentials, session tokens, customer data, or even internal source code. One compromised endpoint can have ripple effects.
People often delay updating browsers or ignore prompts. That delay is exactly what attackers rely on. Because while the vulnerability is known and patched, many users may not have applied the patch yet.

What You Can Do Right Now: Safeguarding Against CVE-2025-10585 and Similar Zero-Days

These are practical, doable steps you can take even without a large security team. They are focused on prevention, detection, and resilience.

1. Update Your Browser Immediately

Make sure all users in your business are using Chrome version 140.0.7339.185/.186 (Windows/macOS) or 140.0.7339.185 (Linux). If you use Chromium-based browsers (Edge, Brave, Opera etc.), watch for their patches and update as soon as available.

2. Enable Automatic Updates

Where possible, enforce automatic updates on browsers. If there are devices you control centrally (e.g. via device management or policy tools), push the update out so users don’t need to do it manually.

3. Minimise Exposure from Untrusted Sites and Downloads

Since zero-day exploits often use malicious or compromised websites (e.g. phishing, watering hole attacks), reduce risk by:

Training staff not to click suspicious links or download unknown files.
Using browser policies/extensions that block or warn on untrusted or unverified websites.
Restricting browser use for admin / privileged tasks to minimal devices or VMs.

4. Use Strong Identity & Session Controls

Even with up-to-date browsers, you can reduce damage from compromise:

Enforce MFA for critical systems and services.
Limit session duration and require reauthentication after inactivity.
Monitor session tokens or logins from unusual locations/devices.

5. Keep Your Device Ecosystem Hardened

Beyond the browser itself:

Ensure operating systems and libraries are up to date. Zero-days in browser engines often exploit lower-level bugs too.
Use endpoint protection and EDR tools that might detect abnormal behaviour arising from exploit attempts.

6. Establish Detection & Response Readiness

Plan ahead for breaches or exploit attempts:

Set up browser version tracking across your device fleet so you can see which machines are still vulnerable.
Maintain logging of browser crashes or unexplained behavior; anomalous crashes after visiting sites might hint at exploit attempts.
Run tabletop exercises: “What do we do when a zero-day is announced?” Who is responsible for patching? How fast can you enforce updates across all users/devices?

7. Educate Your Team

Regular security awareness is important:

Teach staff not only about phishing and social engineering, but about browser security: what update prompts look like, how to check versions, why they matter.
Encourage them to install updates when prompted and report if something looks off after an update (e.g. webpages misbehaving).

Final Thoughts

Zero-day vulnerabilities like CVE-2025-10585 are reminders that no tool is perfect. Attackers move fast, but so can we if we build the right habits. For small businesses, it really comes down to two things: patch promptly and limit the blast radius when something goes wrong.

If this post raised questions about your browser policy, update readiness, or how exposed your team might be, We’d be happy to help you run a quick audit or checklist. At Steel FYI, our goal is to help you stay ahead, not behind.

Stay updated. Stay safe.