CVE-2026-85267 in Cloud Shell
Summary
by MITRE • 10/20/2026
A Cross-Site WebSocket Hijacking vulnerability in Cloud Shell prior to 2026-07-22 on Google Cloud Platform allows an unauthenticated attacker to hijack an active Cloud Shell session and exfiltrate the user's OAuth access token using a cross-origin WebSocket request.
This vulnerability was patched on 22 July 2026, and no customer action is needed.
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Analysis
by VulDB Data Team • 10/20/2026
The identified vulnerability represents a significant security flaw within the Google Cloud Platform's Cloud Shell service, specifically affecting versions released prior to July 22, 2026. This issue falls under the category of Cross-Site WebSocket Hijacking, which is closely related to but distinct from traditional Cross-Site Request Forgery attacks due to its exploitation of persistent, bidirectional communication channels rather than simple HTTP requests. The core technical flaw lies in the insufficient validation of origin headers and lack of robust authentication mechanisms for WebSocket connections initiated by unauthenticated or malicious web pages. When a user with an active Cloud Shell session visits a malicious website crafted by an attacker, that site can programmatically initiate a WebSocket connection to the Cloud Shell endpoint. Because browsers enforce same-origin policies on standard HTTP requests but historically have had more nuanced behaviors regarding WebSocket origins depending on implementation details and configuration, this attack vector allows the malicious script to establish a persistent tunnel into the user's session environment without triggering typical browser security warnings or requiring explicit user interaction beyond visiting the page.
The operational impact of this vulnerability is severe because it enables an unauthenticated attacker to hijack an active Cloud Shell session. Once the WebSocket connection is established, the attacker gains read and write access to the terminal interface running within the cloud environment. This effectively bypasses authentication controls that would normally protect sensitive operations. The primary consequence highlighted in reports is the ability to exfiltrate the user's OAuth access token. These tokens are critical credentials used for authenticating API requests across Google Cloud services. By capturing these tokens, an attacker can impersonate the legitimate user, gaining unauthorized access to a wide range of cloud resources including storage buckets, compute instances, and managed databases. This leads directly to data breaches, potential lateral movement within the organization's infrastructure, and complete compromise of the affected identity's privileges.
From a classification perspective, this vulnerability aligns with CWE-942, which describes Cross-Site WebSocket Hijacking, as well as CWE-384 regarding Session Fixation if the session identifiers are reused or predictable in certain contexts. In terms of adversary tactics and techniques, this attack maps to MITRE ATT&CK technique T1539, specifically Steal Web Session Cookie, although adapted for WebSocket-based token theft rather than traditional cookie stealing. It also relates to T1078, Valid Accounts, as the attacker leverages stolen credentials to maintain persistent access. The lack of proper origin validation and the failure to implement strict CORS policies for WebSocket endpoints are fundamental design oversights that allow this exploitation path to succeed.
Mitigation strategies primarily involve ensuring that all WebSocket connections enforce strict Origin header checks on the server side to reject requests from unauthorized domains. Implementing SameSite attributes on cookies, although less directly applicable to WebSockets than HTTP, remains a good practice for overall session security. For users of Google Cloud Platform, this specific vulnerability was addressed in updates released after July 22, 2026. Consequently, no immediate action is required by customers who have updated their services or are using the latest stable versions of Cloud Shell. However, organizations should continue to monitor for new advisories and ensure that development teams adhere to secure coding standards that prioritize origin validation and token management in real-time communication protocols. Regular security audits focusing on WebSocket implementations can help prevent similar vulnerabilities from being introduced into other parts of an application architecture.