Google has fixed a critical flaw in Chrome that could let a booby-trapped web page run code outside the browser's protective sandbox. The bug, tracked as CVE-2026-121035, is a use-after-free flaw in Chrome's Prerender feature, which loads pages in the background before a user visits them.

The flaw affects Google Chrome versions before 157.0.8103.38. Google shipped the fix in Chrome 157, released on 3 November 2026, which patches 213 security issues in total, seven of them rated Critical. The patched builds are 157.0.8103.38 for Linux and 157.0.8103.38 or 157.0.8103.39 for Windows and Mac.

According to the CVE record, a remote attacker could trigger the flaw by getting a user to open a crafted HTML page. Because the bug sits in Prerender, the browser keeps using memory it has already released, and the attacker can then execute arbitrary code outside the sandbox. The flaw carries a CVSS score of 9.6, placing it among the most severe browser bugs disclosed this year.

Google credited Xinyang Ge of Anthropic, assisted by the company's AI model Claude, with reporting the flaw. Google has not said the bug is being actively exploited, and it is not listed in the US CISA catalogue of known exploited vulnerabilities. Even so, a sandbox escape is the kind of flaw attackers prize, because it removes the layer meant to contain a compromised web page.

Users should check they are on Chrome 157.0.8103.38 or later by opening chrome://version, then relaunch the browser so the update takes effect. Google rolls the release out in stages, so the update may take days to reach every device.