# CVE-2026-66321: Microsoft Edge type confusion vulnerability

Source: https://junglewise.ai/threats/cve-2026-66321-microsoft-edge-type-confusion-vulnerability  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-04. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-66321 · Severity: high · CVSS 7.4 · Published 2026-08-04

Microsoft Edge is a web browser used by millions of users to access the internet and cloud services. A type confusion vulnerability in Edge's rendering engine could allow an attacker to execute arbitrary code on a user's computer by tricking them into visiting a malicious website, potentially compromising personal data, passwords, and system security.

Technologies: [Microsoft Edge](https://junglewise.ai/threats/technologies/edge), [Microsoft Edge Chromium](https://junglewise.ai/threats/technologies/edge-chromium). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-66321 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-66321 being exploited in the wild.

**How severe is CVE-2026-66321?** High severity, with a CVSS score of 7.4, published 4 August 2026.

**Which products and versions are affected?** Microsoft Edge Chromium-based versions.

**Is there a fix for CVE-2026-66321?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-66321 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-66321?** Check whether you run Microsoft Edge or Microsoft Edge Chromium at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A type confusion vulnerability exists in Microsoft Edge (Chromium-based) where incompatible resource types are accessed without proper validation. This vulnerability is in the browser's rendering or JavaScript engine and can be triggered remotely over a network when a user visits a malicious webpage. No authentication is required for exploitation. A successful attack allows remote code execution with the privileges of the logged-in user. Patches are expected to be available through Microsoft's regular security update cycle.

## Affected products

- Microsoft Edge Chromium-based versions

## Timeline

- 2026-08-04: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66321](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66321)

## Related threats

- [Microsoft Edge out-of-bounds read information disclosure](https://junglewise.ai/threats/cve-2026-122518-out-of-bounds-read-in-microsoft-edge-chromium-based-allows-an)
- [Microsoft Edge privilege escalation via incorrect authorization](https://junglewise.ai/threats/cve-2026-69446-incorrect-authorization-in-microsoft-edge-chromium-based-allows)
- [Microsoft Edge use-after-free privilege elevation](https://junglewise.ai/threats/cve-2026-96203-use-after-free-in-microsoft-edge-chromium-based-allows-an)
- [Microsoft Edge heap-based buffer overflow](https://junglewise.ai/threats/cve-2026-96199-heap-based-buffer-overflow-in-microsoft-edge-chromium-based)
- [Microsoft Edge heap-based buffer overflow](https://junglewise.ai/threats/cve-2026-96198-heap-based-buffer-overflow-in-microsoft-edge-chromium-based)