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CVE-2026-9891 Google CVE debrief

A critical use-after-free vulnerability in Google Chrome's Extensions subsystem allows sandbox escape from a compromised renderer process. The flaw (CWE-416) affects Chrome versions prior to 148.0.7778.216. An attacker who has already achieved renderer compromise can leverage this vulnerability to escape the Chrome sandbox by manipulating extension objects after they have been freed. Google has assigned Chromium security severity: Critical. The vulnerability was disclosed in the May 2026 Stable Channel update.

Vendor
Google
Product
Chrome
CVSS
CRITICAL 9
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-28
Original CVE updated
2026-05-29
Advisory published
2026-05-28
Advisory updated
2026-05-29

Who should care

Organizations with Chrome deployments, particularly those allowing extension installation or with users who may visit untrusted web content. Security teams should prioritize due to Critical severity and active exploitation potential from renderer compromise. Enterprise environments with BYOD policies or less restricted browsing should treat as urgent.

Technical summary

This vulnerability exists in Chrome's extension handling code where a use-after-free condition can be triggered. The attack requires prior compromise of the renderer process, which typically occurs through malicious web content. Once the renderer is compromised, the attacker can exploit this flaw to corrupt freed extension objects, leading to memory corruption that enables escape from Chrome's sandbox. The sandbox normally restricts renderer processes from accessing the host system; successful escape grants broader system access. The fix in Chrome 148.0.7778.216 addresses the underlying memory management issue in the Extensions subsystem.

Defensive priority

critical

Recommended defensive actions

  • Update Google Chrome to version 148.0.7778.216 or later immediately
  • Prioritize patching on endpoints with untrusted extension installations or developer mode enabled
  • Monitor for suspicious extension activity, particularly from non-Chrome Web Store sources
  • Review extension permissions and remove unnecessary or unused extensions
  • Enable site isolation and enhanced safe browsing if not already configured
  • Consider enterprise policies to restrict extension installation to allowlisted sources only

Evidence notes

CVE description confirms use-after-free in Extensions with sandbox escape potential. Chromium security severity rated Critical. Affected versions explicitly stated as prior to 148.0.7778.216. CWE-416 (Use After Free) identified in NVD metadata.

Official resources

2026-05-28