CVE-2026-9116: Chrome ServiceWorker Data Leak Vulnerability

CVE-2026-9116 Overview

CVE-2026-9116 is an insufficient policy enforcement vulnerability in the ServiceWorker component of Google Chrome versions prior to 148.0.7778.179. A remote attacker can leak cross-origin data by tricking a user into visiting a crafted HTML page. The flaw is tracked under [CWE-693] (Protection Mechanism Failure) and exploitation requires user interaction. Chromium engineers rated the security severity as High, while NVD assigns a CVSS 3.1 base score of 4.3.

Critical Impact

A remote attacker can bypass same-origin protections enforced by ServiceWorker and exfiltrate cross-origin data from a victim's browser session.

Affected Products

• Google Chrome desktop versions prior to 148.0.7778.179
• Chromium-based browsers sharing the same ServiceWorker implementation
• All supported desktop platforms (Windows, macOS, Linux) running affected Chrome builds

Discovery Timeline

• 2026-05-20 - CVE-2026-9116 published to NVD
• 2026-05-20 - Last updated in NVD database

Technical Details for CVE-2026-9116

Vulnerability Analysis

The vulnerability resides in Chrome's ServiceWorker subsystem. ServiceWorkers are background scripts that intercept network requests for a registered scope and operate independently of the page that registered them. Chrome must enforce origin and request-mode policies to prevent a ServiceWorker from accessing or revealing content belonging to a different origin.

In affected builds, Chrome fails to fully enforce these policies. A crafted HTML page can cause the browser to expose data from a cross-origin response that should have been opaque to the attacker-controlled script. The result is a violation of the Same-Origin Policy, leading to confidentiality loss without integrity or availability impact.

The attacker must convince the user to load a malicious page, which limits weaponization compared to zero-click flaws. However, drive-by delivery through advertising, search results, or phishing remains practical.

Root Cause

The root cause is a Protection Mechanism Failure [CWE-693] in the ServiceWorker request-handling logic. The browser does not consistently apply cross-origin read-blocking checks to certain response types or fetch modes routed through the ServiceWorker, allowing the registered worker to observe data it should not see.

Attack Vector

Exploitation proceeds over the network and requires user interaction. The attacker hosts a page that registers or interacts with a ServiceWorker, then issues fetches that target sensitive cross-origin endpoints, such as authenticated APIs or HTML pages from sites where the victim is logged in. Because policy enforcement is insufficient, the ServiceWorker reads or measures response data and returns it to the attacker's origin.

The vulnerability does not grant code execution, privilege escalation, or persistence. Its value to attackers lies in reconnaissance, session token theft, and harvesting authenticated content. Refer to the Chromium Issue Report #497436273 and the Google Chrome Desktop Update for vendor details.

Detection Methods for CVE-2026-9116

Indicators of Compromise

• Browser telemetry showing Chrome versions older than 148.0.7778.179 in the enterprise fleet.
• Outbound HTTP requests from browser sessions to attacker-controlled domains containing payloads that resemble authenticated content from third-party sites.
• ServiceWorker registrations from low-reputation or newly observed domains preceding suspicious cross-origin data flows.

Detection Strategies

• Inventory installed Chrome versions across endpoints and flag any build older than 148.0.7778.179.
• Monitor web proxy and DNS logs for connections to newly registered domains that subsequently issue large volumes of cross-origin fetches.
• Hunt for browser process anomalies, such as renderer processes making unusual outbound POSTs containing base64 or JSON blobs after visiting unfamiliar sites.

Monitoring Recommendations

• Forward browser endpoint telemetry and proxy logs into a centralized analytics platform to correlate version data with suspicious egress.
• Track the Chrome stable channel release feed and enforce automatic updates through enterprise management policies.
• Review ServiceWorker registrations on managed devices using browser enterprise reporting where available.

How to Mitigate CVE-2026-9116

Immediate Actions Required

• Update Google Chrome to version 148.0.7778.179 or later on all managed endpoints.
• Restart Chrome after the update so the new binary and ServiceWorker runtime take effect.
• Verify Chromium-based browsers in the environment have ingested the corresponding upstream fix.

Patch Information

Google addressed CVE-2026-9116 in Chrome stable channel build 148.0.7778.179. Full details are available in the Google Chrome Desktop Update advisory and the underlying Chromium Issue Report #497436273. Administrators should ensure auto-update is enabled and confirm version compliance through endpoint management tooling.

Workarounds

• Restrict browsing to trusted sites using enterprise URL allow-lists until the patch is deployed.
• Disable or restrict ServiceWorker registration on sensitive corporate browser profiles where feasible.
• Train users to avoid clicking links from untrusted sources, since exploitation requires loading an attacker-controlled page.