CVE-2026-13838: Google Chrome Auth Bypass Vulnerability

CVE-2026-13838 Overview

CVE-2026-13838 is a same-origin policy bypass in Google Chrome caused by an inappropriate implementation in the browser's CSS engine. The flaw affects Chrome versions prior to 150.0.7871.47 and is classified under [CWE-346] Origin Validation Error. A remote attacker can exploit the issue by luring a user to a crafted HTML page, allowing cross-origin data to be accessed in violation of the same-origin policy. Google's Chromium security team rated the internal severity as High, while the NVD assigns a base score of 6.5.

Critical Impact
Successful exploitation lets attacker-controlled pages read or influence data from other origins, undermining the browser's fundamental isolation boundary between websites.

Affected Products

Google Chrome for Desktop prior to 150.0.7871.47
Chromium-based browsers that inherit the vulnerable CSS implementation
All operating systems supported by the Chrome Stable channel

Discovery Timeline

2026-06-30 - CVE-2026-13838 published to NVD
2026-07-02 - Last updated in NVD database

Technical Details for CVE-2026-13838

Vulnerability Analysis

The vulnerability resides in Chrome's CSS engine, where an inappropriate implementation permits a crafted HTML page to bypass the same-origin policy (SOP). The SOP is the core browser boundary that prevents a document loaded from one origin from reading or manipulating resources served by another. When this control fails inside a rendering subsystem such as CSS, attacker-controlled pages gain a channel to observe or infer cross-origin content that should remain inaccessible.

The CVSS vector indicates a network-reachable attack requiring user interaction, with a high integrity impact and no direct confidentiality or availability effect on the host. In practice, the integrity impact reflects the ability to corrupt the trust boundary between origins rather than to modify files on disk. The EPSS probability is 0.186%, placing the CVE in the lower percentile of exploitation likelihood at publication time.

Root Cause

The root cause is an origin validation error [CWE-346] in how the CSS subsystem handles resources or state that cross security origins. The engine treats certain CSS-related operations without fully enforcing the origin checks the SOP requires, exposing cross-origin data through the rendering path.

Attack Vector

Exploitation requires a victim to visit or interact with an attacker-controlled HTML page. The page delivers crafted CSS constructs that exercise the flawed code path, causing the browser to leak cross-origin information or perform actions across the origin boundary. No authentication or elevated privileges are required on the target system.

No public proof-of-concept, exploit code, or CISA KEV listing is available for CVE-2026-13838. Technical detail is tracked in the Chromium Issue Tracker Entry.

Detection Methods for CVE-2026-13838

Indicators of Compromise

Chrome desktop clients reporting a version below 150.0.7871.47 in inventory or user-agent telemetry.
Outbound requests to newly registered or low-reputation domains hosting HTML pages with unusual CSS payloads.
Browser telemetry showing repeated navigations to pages that load cross-origin stylesheets from untrusted sources.

Detection Strategies

Query endpoint software inventory for installed Chrome builds and flag any version earlier than 150.0.7871.47.
Correlate proxy and DNS logs with threat intelligence feeds to identify user visits to suspicious HTML lures.
Review Chrome enterprise reporting for crash or rendering anomalies coinciding with visits to untrusted domains.

Monitoring Recommendations

Enable Chrome Enterprise reporting and forward browser telemetry to a centralized logging platform.
Alert on user browsing sessions where cross-origin CSS resources originate from domains outside sanctioned application allowlists.
Track patch compliance for Chrome across managed endpoints and re-scan after each Stable channel release.

How to Mitigate CVE-2026-13838

Immediate Actions Required

Update Google Chrome to version 150.0.7871.47 or later on all managed endpoints.
Force-restart Chrome after deployment to ensure the patched binaries are loaded in active sessions.
Verify that Chromium-based derivatives in the environment have picked up the corresponding upstream fix.

Patch Information

Google addressed CVE-2026-13838 in the Chrome Stable channel release referenced in the Google Chrome Update Announcement. Administrators should ensure Chrome auto-update is enabled and confirm that endpoints report the fixed build. Additional technical context is available in the Chromium Issue Tracker Entry.

Workarounds

Restrict browsing to trusted domains via web filtering or Chrome Enterprise URL allowlists until patching completes.
Enforce Site Isolation and disable unnecessary browser features on high-risk user groups.
Educate users to avoid clicking links from unsolicited email or messaging while updates are being rolled out.

bash

# Configuration example: enforce minimum Chrome version via Chrome Enterprise policy (Linux master_preferences)
# /etc/opt/chrome/policies/managed/chrome_min_version.json
{
  "MinimumChromeVersion": "150.0.7871.47",
  "RestrictSigninToPattern": ".*@example\\.com",
  "URLAllowlist": [
    "https://*.example.com"
  ],
  "SitePerProcess": true
}