A cross‑site WebSocket hijacking flaw in Google Cloud Shell allowed an unauthenticated attacker to hijack an active Cloud Shell session and exfiltrate the user’s OAuth access token through a cross‑origin WebSocket request. The vulnerability is a classic instance of improper handling of origin information, classified as CWE‑1385. By obtaining the OAuth token the attacker could potentially impersonate the victim in downstream services, leading to privilege escalation or data exfiltration.

This issue affected the Google Cloud Platform’s Cloud Shell before the 2026‑07‑22 release. No specific version numbers beyond the release date are listed, but all Cloud Shell users prior to that patch date were vulnerable.

The CVSS score of 8.7 denotes high severity, while the very low EPSS score (< 1 %) indicates that exploitation is currently unlikely. The vulnerability was not listed in CISA’s KEV catalog, underscoring that no known exploits are in widespread use. The likely attack vector involves a malicious web page issuing a cross‑origin WebSocket connection to an authenticated Cloud Shell session; this inference is based on the description of the flaw. Users with patched Cloud Shell (post‑22 July 2026) are no longer at risk.