CVE-2026-78942: Google Chrome Auth Bypass Vulnerability

CVE-2026-78942 Overview

CVE-2026-78942 is an incorrect reference resolution vulnerability in the Loader component of Google Chrome prior to version 152.0.7977.65. A remote attacker can bypass the web origin policy by delivering crafted network traffic to a targeted browser. Google's Chromium project rates the security severity as Medium. The flaw is classified under CWE-706: Use of Incorrectly-Resolved Name or Reference. Successful exploitation enables cross-origin data access, breaking the fundamental isolation boundary that separates web origins in the browser. The issue is tracked in the Chromium bug database as Issue 502139081 and was addressed in the Stable Channel desktop update.

Critical Impact
Attackers can bypass same-origin protections and access resources belonging to unrelated web origins through crafted network traffic.

Affected Products

Google Chrome desktop versions prior to 152.0.7977.65
Chromium-based browsers that ship the vulnerable Loader implementation
Embedded WebView and CEF components sharing the affected Loader code

Discovery Timeline

2026-08-25 - CVE-2026-78942 published to the National Vulnerability Database
2026-08-26 - Last updated in the NVD database

Technical Details for CVE-2026-78942

Vulnerability Analysis

The defect lives in Chrome's Loader, the subsystem responsible for fetching, dispatching, and associating network responses with the correct document, worker, or subresource context. Under specific conditions, the Loader resolves an internal reference to the wrong originating context. That mismatch causes the browser to treat a response as if it belonged to a different web origin than the one that actually initiated or should govern the request.

Web origin policy enforcement depends on the Loader consistently associating each response with the correct security principal. When the reference resolution step returns an incorrect target, downstream checks in the network stack and renderer operate on stale or wrong origin metadata. This is a textbook manifestation of CWE-706, where a name or reference maps to an unintended entity.

Root Cause

The root cause is an incorrect reference resolution within the Loader. The component looks up an object, request, or context by an identifier and returns a reference that does not correspond to the intended origin-bound entity. Consult the Chromium Issue Tracker #502139081 for implementation-level details.

Attack Vector

Exploitation is remote and network-based. A remote attacker crafts specific network traffic, typically a sequence of HTTP responses or resource loads, and induces the victim browser to process that traffic. The malformed sequence steers the Loader toward the incorrect reference, allowing the attacker's origin to observe or interact with data scoped to a different origin. No verified public proof-of-concept has been published, and the Exploit Prediction Scoring System places this issue in a low-probability range at the time of publication.

No verified code examples are available. See the Google Chrome Stable Update advisory for the vendor description of the fix.

Detection Methods for CVE-2026-78942

Indicators of Compromise

Chrome desktop clients reporting a version string below 152.0.7977.65 in browser telemetry or user-agent logs.
Web application logs showing cross-origin resource access patterns that do not align with expected CORS preflight sequences.
Unusual response header combinations, such as mismatched Content-Type or Origin values, arriving from attacker-controlled hosts during active browsing sessions.

Detection Strategies

Inventory installed Chrome and Chromium-derivative versions across managed endpoints and flag any build older than 152.0.7977.65.
Correlate browser version telemetry with web proxy logs to identify users visiting untrusted sites while running an unpatched browser.
Hunt for anomalous fetches to sensitive internal origins immediately following navigation to external, low-reputation domains.

Monitoring Recommendations

Enable central logging of browser version data through enterprise management tools and Chrome Browser Cloud Management.
Forward web proxy and DNS logs into a security data lake, then alert on cross-origin data flows that violate documented application boundaries.
Track Chromium security release notes and Chromium Issue Tracker updates for follow-on issues in the Loader component.

How to Mitigate CVE-2026-78942

Immediate Actions Required

Update Google Chrome to version 152.0.7977.65 or later on all Windows, macOS, and Linux endpoints.
Verify that automatic browser updates are enabled and functioning, and force a relaunch on hosts that have deferred restarts.
Audit Chromium-based applications, including Electron builds and embedded WebViews, and upgrade them to a release that incorporates the fixed Loader code.

Patch Information

Google addressed CVE-2026-78942 in the Chrome Stable Channel with the release of version 152.0.7977.65. Details are available in the Google Chrome Stable Update advisory and the corresponding Chromium Issue Tracker #502139081 entry. Administrators managing fleets should push the update through Chrome Browser Cloud Management, Group Policy, MDM profiles, or the operating system package manager.

Workarounds

No vendor-supplied workaround exists; patching is the authoritative remediation.
Restrict browsing on unpatched endpoints to trusted internal origins until the update is deployed.
Apply web proxy rules that block access to unclassified or newly registered domains to reduce exposure to crafted responses during the patch window.

bash

# Verify installed Chrome version on Linux endpoints
google-chrome --version

# Windows: query the installed version from the registry
reg query "HKLM\SOFTWARE\WOW6432Node\Google\Update\Clients\{8A69D345-D564-463C-AFF1-A69D9E530F96}" /v pv

# macOS: read the version from the application bundle
defaults read "/Applications/Google Chrome.app/Contents/Info.plist" CFBundleShortVersionString