CVE-2025-6554: Understanding the Vulnerability and Its Impact

Disclosure & Exploitation Status

Google disclosed CVE-2025-6554 on June 25, 2025. This vulnerability is a type confusion vulnerability in the V8 JavaScript/WebAssembly engine. Within hours of the disclosure, Google confirmed that it was actively exploited in the wild, targeting users through malicious webpages.

• June 25, 2025 – Reported by Google TAG, confirmed exploited.

• June 26, 2025 – Emergency mitigation via configuration update.

• July 2, 2025 – Full patch released in Chrome 138.0.7204.96/.97 (Windows), 138.0.7204.92/.93 (macOS), 138.0.7204.96 (Linux).

• July 2, 2025 – Added to CISA’s Known Exploited Vulnerabilities catalog, patch deadline: July 23, 2025.

  
  

Because Chromium powers browsers like Edge, Brave, and Opera, this vulnerability extends beyond Chrome itself.

Attacker POV: How CVE-2025-6554 Works

At a technical level, the bug arises from temporal confusion in V8 when handling `let` variable declarations combined with optional chaining. Improper ordering and reference handling enable invalid dereferences and potential use-after-free conditions.

A malicious webpage can exploit this behavior to:

• Achieve arbitrary memory read/write.

• Execute attacker-supplied shellcode in the renderer process.

• Escape Chrome’s sandbox (via chaining with other flaws).

• Drop malware, steal credentials, or spy on user activity.

  
  

Ghost Ops PoC: Safe Exploit Harness

To validate the issue in Chromium 137.0.7151.67, we created a non-weaponized PoC harness to stress the vulnerable V8 logic.

Step 1 — Local Web Server

We served crafted HTML/JS using Python’s HTTP server:

Step 2 — Crash-Test Harness

We built an HTML file (uaf-test.html) that stresses memory allocation and garbage collection.

We launched Chrome against the harness with hardened flags:

Step 3 — CVE-2025-6554 Trigger PoC

Next, we ran a minimal JS snippet designed to highlight the temporal confusion bug.

• Expected (patched Chrome) → ReferenceError logged.

• Observed (vulnerable Chrome) → abnormal return value, renderer crash (Aw Snap! error 5), or memory corruption symptoms.

  
  

This confirmed:

1. Our harness executed.

2. Chrome 137.0.7151.67 was vulnerable.

3. The bug triggered a crash consistent with UAF/type confusion.

   
   

What This Means (Impact)

Attack Surface

Any user visiting a malicious site could be exploited with zero interaction. This is a significant risk.

Outcome

The result is Remote Code Execution, which can lead to potential sandbox escape and system compromise.

Adversary Utility

This vulnerability is useful for cybercrime, including credential theft, spyware, and ransomware. It also poses risks for espionage, such as surveillance of journalists, activists, and executives.

Broader Ecosystem Risk

Chromium-based browsers (Edge, Brave, Opera) all inherit this flaw. This makes the impact widespread and critical.

Defender POV: Mitigation Steps

1. Patch immediately: Update Chrome to 138.0.7204.96+ (or later) and enforce updates in enterprise environments.

2. Apply KEV Guidance: Per CISA, the remediation deadline was July 23, 2025. Non-compliance risks regulatory penalties.

3. Threat Hunting: Monitor for anomalous browser crashes, unexpected child processes, or suspicious GPU behavior.

4. Browser Hardening: Apply stricter browsing controls in sensitive environments (containerized sessions, RBAC).

5. Educate Users: Train staff to recognize malvertising and drive-by download risks.

   
   

Business Risk & Takeaway

The Browser as the Front Door

Chrome zero-days like CVE-2025-6554 can bypass traditional security tools. The browser is the front door for business operations. Exploitation means credential theft, data exfiltration, and ransomware are only one click away.

Patching is Not Optional

For enterprises, patching is not optional. Delays create exploitable attack windows measured in hours.

Ghost Ops Final Word

At Ghost Ops, we don’t just read advisories—we build safe PoCs to validate how these vulnerabilities behave in real-world attack chains. By doing so, we expose whether your defenses detect and respond appropriately before adversaries weaponize the same bugs.

CVE-2025-6554 is the fourth Chrome zero-day this year alone. Browser security remains one of the most critical blind spots in enterprise defense.

Patch now. Test your defenses. Assume exploitation is already happening. Ghost Ops can simulate CVE-2025-6554 exploitation safely within your environment so you know exactly how prepared you are.

Stay ahead of threats.