Chrome V8: Type confusion in V8 engine leading to arbitrary read/write (CVE-2025-6554) #shorts
Summary
Welcome to today’s cybersecurity podcast. In this episode, we’ll discuss CVE-2025-6554, a high-severity zero-day vulnerability in Google Chrome’s V8 JavaScript engine. This flaw has been actively exploited in the wild and is the fourth Chrome zero-day patched by Google in 2025.
Product details
The vulnerability affects Google Chrome versions prior to 138.0.7204.96 on all supported platforms. Chrome’s Stable Channel was updated to versions 138.0.7204.96 and 138.0.7204.97, which include the security fix. A corresponding advisory was also issued for Debian’s Chromium package to mitigate potential code execution or information disclosure on Debian-based systems.
Vulnerability type summary
CVE-2025-6554 is classified as a Type Confusion issue in the V8 engine. Type confusion arises when the engine misinterprets the data type of an object or variable, leading to unintended behavior such as reading or writing outside of memory bounds.
Details of the vulnerability
By crafting a malicious HTML page, an attacker can trigger the type confusion bug in V8 to gain arbitrary read and write access to memory. With these primitives, the attacker can escalate privileges, execute arbitrary code, or steal sensitive data in the context of the browser process. Google confirmed active exploitation prior to patch release, prompting an emergency update. The Chromium security team rated this flaw as High severity due to the ease of exploitation and potential impact.
Conclusion
If you use Google Chrome or Debian’s Chromium, update immediately to Chrome 138.0.7204.96 or later—or apply your distribution’s security update—to protect against CVE-2025-6554. Stay vigilant for future advisories and always keep your browser current to defend against emerging zero-day threats.
Watch the full video on YouTube: CVE-2025-6554
Remediation and exploitation details
This chain involves the following actors
- Remote attacker: External threat orchestrating the exploit
This following systems are involved
- Chrome V8 JavaScript engine (Executes JavaScript code in Chromium-based browsers): Vulnerable component subject to type-confusion bug
- User workstation (Runs the web browser): Target for arbitrary code execution after memory corruption
Attack entry point
- Malicious HTML page: HTML page containing specially crafted JavaScript that triggers type confusion in the V8 engine when loaded
Remediation actions
Exploitation actions
Type confusion through manipulated hidden class maps
- const obj = { a: 1 };
- obj.b = 2; // Force hidden class change
- /* Insert code to overlap element array pointer with inline property storage */
User navigates to attacker-controlled site
- <!DOCTYPE html>
- <html><body><script src="exploit.js"></script></body></html>
Automatic script execution upon page load
- triggerConfusion();
- let leaked = read64(fakeObject); // Read arbitrary memory
- write64(fakeObject, shellcodeAddress); // Write to prepare for code execution
Privilege escalation from JavaScript context to native code execution
- overwriteJITCode(ptr, shellcodeBuffer);
- invokeShellcode();
Related Content
NOTE: The following related content has not been vetted and may be unsafe.
- https://chromereleases.googleblog.com/2025/06/stable-channel-update-for-desktop_30.html
- https://issues.chromium.org/issues/427663123
- [2025-07-01] Chrome Stable Channel Update 138.0.7204.96/.97 includes a security fix for CVE-2025-6554.
- [2025-07-01] Critical vulnerability CVE-2025-6554 in Google Chrome V8 component allows for elevated rights exploitation; upgrade recommended.
- [2025-07-02] Google releases an emergency fix for a high-severity zero-day vulnerability in Chrome, CVE-2025-6554.
- [2025-07-02] Google patches fourth Chrome zero-day vulnerability in 2025, CVE-2025-6554, with an exploit in the wild.
- [2025-07-02] Debian security advisory warns of a critical vulnerability in Chromium that could lead to code execution, denial of service, or information disclosure.