A flaw in Google Chrome’s WebUI on Linux, macOS, Windows, and ChromeOS allowed a remote attacker who had already compromised the renderer process to bypass the browser’s site isolation boundary. By navigating to a specially crafted HTML page, the attacker could evict the isolation protection that normally keeps separate site processes from accessing each other’s data, thereby elevating privileges and potentially accessing sensitive data from another site or compromising the browser process. The vulnerability is identified as a medium severity issue in Chromium’s own ranking and represents an improper authorization weakness.

Affected versions are all releases of Google Chrome prior to 148.0.7778.96 on Linux, macOS, Windows and ChromeOS. Any workstation or device using a pre―148.0.7778.96 build is potentially vulnerable.

The EPSS score is not available, and the vulnerability is not listed in CISA’s KEV catalog, indicating no public exploitation evidence. The CVSS base score of 4.3 indicates low―to―moderate risk, which aligns with Chromium’s medium severity classification. The likely attack vector is a compromised renderer process, which could arise from a broader compromise or a prior vulnerability that grants code execution in the renderer context.