CVE-2026-13839: Google Chrome Auth Bypass Vulnerability

CVE-2026-13839 Overview

CVE-2026-13839 is a same-origin policy bypass in the Cascading Style Sheets (CSS) implementation of Google Chrome. The flaw affects Chrome versions prior to 150.0.7871.47 and is tracked under [CWE-346: Origin Validation Error]. A remote attacker can bypass the same-origin policy by luring a user to a crafted HTML page. Google's Chromium team assigned the underlying issue a High security severity rating.

The vulnerability allows cross-origin data confusion or injection through CSS handling, undermining a core browser security boundary. Exploitation requires user interaction, typically visiting an attacker-controlled site.

Critical Impact
Successful exploitation lets a remote attacker bypass the same-origin policy, enabling cross-origin reads or integrity violations against sites the victim visits.

Affected Products

Google Chrome versions prior to 150.0.7871.47
Chromium-based browsers sharing the same CSS engine code path
Desktop Stable channel builds on Windows, macOS, and Linux

Discovery Timeline

2026-06-30 - CVE-2026-13839 published to NVD
2026-07-02 - Last updated in NVD database

Technical Details for CVE-2026-13839

Vulnerability Analysis

The defect resides in Chrome's CSS implementation, where an inappropriate implementation permits cross-origin interactions that the same-origin policy should block. CSS is loaded permissively across origins by design, but the browser must still isolate style computation, resource fetching, and side-channel signals between origins. This vulnerability breaks that isolation.

A crafted HTML page can cause the CSS engine to expose or accept data across origin boundaries. The classification as [CWE-346] indicates the engine fails to correctly validate the origin of a resource, response, or computation. The attack vector is network-based and does not require authentication, but it does require the victim to open a malicious page.

The integrity impact is high, while confidentiality and availability are unaffected in the scored vector. This aligns with attacks that inject or alter cross-origin state without directly disclosing memory contents.

Root Cause

The root cause is missing or incorrect origin validation inside a CSS processing path. Chromium tracks the specific defect in Chromium Issue 514449396. Details are restricted while patch adoption continues.

Attack Vector

An attacker hosts a malicious page that references cross-origin resources through CSS constructs. When the victim visits the page, the browser processes styles in a way that leaks or alters cross-origin state. No credentials, elevated privileges, or local access are required beyond a single user click or navigation.

No verified public exploit or proof-of-concept has been published. See the Google Chrome Update Announcement for the vendor's release notes.

Detection Methods for CVE-2026-13839

Indicators of Compromise

Outbound Chrome connections from endpoints running versions earlier than 150.0.7871.47 to newly registered or low-reputation domains
HTML pages containing unusual cross-origin @import, url(), or font-face CSS references pointing to sensitive internal endpoints
Browser telemetry showing anomalous cross-origin resource loads immediately after navigation to untrusted sites

Detection Strategies

Inventory browser versions across managed endpoints and flag Chrome installations below 150.0.7871.47
Inspect web proxy and DNS logs for user navigation to unknown domains followed by rapid cross-origin fetches to internal applications
Correlate endpoint process telemetry with URL categorization data to surface users visiting suspicious sites while running vulnerable Chrome builds

Monitoring Recommendations

Enforce browser version reporting through enterprise management and alert when hosts fall behind the fixed build
Monitor for phishing campaigns or malvertising that direct users to crafted HTML pages targeting Chrome
Track EPSS movement for CVE-2026-13839, currently 0.186% at percentile 8.343, and reassess prioritization if exploit activity emerges

How to Mitigate CVE-2026-13839

Immediate Actions Required

Update Google Chrome to version 150.0.7871.47 or later on all managed endpoints
Restart the browser after update to ensure the patched binaries are loaded
Apply equivalent updates to Chromium-based browsers once their vendors ship the fix

Patch Information

Google released the fix in the Chrome Stable channel update documented in the Google Chrome Update Announcement. The corresponding Chromium defect is tracked in the Chromium Issue Tracker Entry. Administrators should validate deployment through enterprise policy tools such as Chrome Browser Cloud Management.

Workarounds

Restrict browsing to trusted sites through web filtering until patching is complete
Use enterprise policies to enable automatic updates and prevent users from delaying browser restarts
Deploy site isolation and strict Content Security Policy (CSP) directives on internal applications to reduce cross-origin exposure

bash

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

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