The vulnerability arises from insufficient validation of untrusted input within Chrome’s SiteIsolation component. In versions earlier than 148.0.7778.96 a specially crafted HTML document can trick the renderer process into treating data from one origin as if it were from another. This allows an attacker who has already compromised the renderer to read or otherwise manipulate information belonging to a protected site, effectively sidestepping Chrome’s isolation safeguards.

The flaw affects all installations of Google Chrome running any operating system prior to version 148.0.7778.96. It applies to the stable channel and any prior builds that have not received the official fix.

The vulnerability is labeled as Medium severity by Chromium, with a CVSS score of 3.1, no EPSS score is available, and it is not listed in the CISA KEV catalog. The attack requires the attacker to first compromise the renderer process, which can be achieved through malicious web content or malicious extensions. Although this raises the effort barrier, the presence of a feasible attack vector means that organizations should prioritize updating Chrome to the patched release.