CVE-2026-78894: Google Chrome Race Condition Vulnerability

CVE-2026-78894 Overview

CVE-2026-78894 is a race condition vulnerability in the Payments component of Google Chrome prior to version 152.0.7977.65. An attacker who has already compromised the renderer process can leak cross-origin data by serving a crafted HTML page to a user. Google's Chromium team classified the security severity as Medium, while NVD assigns a Low base score reflecting the requirement for a pre-compromised renderer and user interaction. The flaw is tracked as CWE-367: Time-of-check Time-of-use (TOCTOU).

Critical Impact
A remote attacker with a compromised renderer process can exploit a timing window in Chrome's Payments code to read cross-origin data, breaking the same-origin policy that isolates web content.

Affected Products

Google Chrome desktop versions prior to 152.0.7977.65
Chromium-based browsers that ship the vulnerable Payments component
Downstream distributions bundling pre-patch Chromium releases

Discovery Timeline

2026-08-25 - CVE-2026-78894 published to the National Vulnerability Database
2026-08-27 - Last updated in NVD database

Technical Details for CVE-2026-78894

Vulnerability Analysis

The vulnerability resides in the Payments subsystem of Chrome, which handles Web Payment API interactions between the renderer and browser processes. A race condition allows an attacker to manipulate the state of a payment-related resource between the time it is validated and the time it is used. This is a classic Time-of-check Time-of-use (TOCTOU) pattern tracked as CWE-367.

Exploitation is not straightforward. The attacker must already control the renderer process, typically through a separate renderer-side bug, and must win a narrow timing window. Success yields the ability to read cross-origin data that the Payments code path handles, undermining Chrome's site isolation guarantees for that data.

Root Cause

The root cause is missing or insufficient synchronization around a shared resource inside the Payments component. Two concurrent code paths access the same state without ordering guarantees, allowing an attacker-controlled renderer to swap or mutate the resource between validation and use. The result is a boundary violation where cross-origin content is exposed to a context that should not see it.

Attack Vector

The attack is remote and requires user interaction such as visiting an attacker-controlled page. It also requires a prior renderer compromise, which raises the practical exploitation bar. Once those preconditions are met, the attacker triggers Payments API operations from the crafted page and races the vulnerable code path to observe data from another origin. Refer to the Chromium Issue Tracker entry 505991181 and the Google Chrome desktop update announcement for vendor detail.

No public proof-of-concept or exploit code is available at this time.

Detection Methods for CVE-2026-78894

Indicators of Compromise

Chrome browser processes running versions below 152.0.7977.65 on managed endpoints.
Renderer process crashes or unexpected child process spawns preceding payment-related page loads.
Outbound connections to unfamiliar domains that host Web Payments API interactions in short succession.

Detection Strategies

Inventory installed Chrome versions across the fleet and flag any build older than 152.0.7977.65.
Correlate renderer process anomalies with visits to untrusted origins that invoke PaymentRequest APIs.
Alert on chained behavior where a renderer exploit indicator is followed by cross-origin data access patterns in browser telemetry.

Monitoring Recommendations

Ingest browser and endpoint telemetry into a centralized data lake for version and behavior analytics.
Track Chrome auto-update health to ensure clients receive the fixed build promptly.
Monitor security bulletin feeds from the Chrome Releases blog for related follow-up fixes.

How to Mitigate CVE-2026-78894

Immediate Actions Required

Update Google Chrome to version 152.0.7977.65 or later on all Windows, macOS, and Linux endpoints.
Restart the browser after update to ensure the patched Payments component is loaded.
Verify that Chrome auto-update is enabled and reachable through corporate proxies and firewalls.

Patch Information

Google released the fix in the Chrome stable channel update documented in the Chrome Releases desktop advisory. Administrators should push Chrome 152.0.7977.65 or newer through their existing software deployment tooling. Chromium-based browsers should be updated once vendors integrate the upstream fix.

Workarounds

Restrict use of the Web Payments API through enterprise policy where feasible until patching completes.
Enforce site isolation and strict same-origin policies via Chrome enterprise configuration.
Limit user browsing to trusted origins on high-value systems until the patched build is deployed.

bash

# Verify installed Chrome version on Linux and macOS endpoints
google-chrome --version
# Expected output: Google Chrome 152.0.7977.65 or later

# Windows: query the installed version from the registry
reg query "HKLM\Software\Google\Update\Clients\{8A69D345-D564-463C-AFF1-A69D9E530F96}" /v pv