CVE-2026-7977: Google Chrome Auth Bypass Vulnerability

CVE-2026-7977 Overview

CVE-2026-7977 is a same-origin policy bypass in the Canvas component of Google Chrome versions prior to 148.0.7778.96. A remote attacker can craft a malicious HTML page that abuses the Canvas implementation to read or interact with cross-origin resources. The flaw maps to [CWE-269: Improper Privilege Management] and affects Chrome on Windows, macOS, and Linux. Google rates the Chromium security severity as Medium and addressed the issue in the May 2026 stable channel update. Exploitation requires user interaction, such as visiting an attacker-controlled web page.

Critical Impact

A remote attacker can bypass the same-origin policy through crafted HTML, exposing cross-origin content rendered via the Canvas API.

Affected Products

• Google Chrome versions prior to 148.0.7778.96
• Chrome on Microsoft Windows, Apple macOS, and Linux
• Chromium-derived browsers that have not integrated the upstream fix

Discovery Timeline

• 2026-05-06 - CVE-2026-7977 published to NVD
• 2026-05-06 - Last updated in NVD database
• May 2026 - Google releases stable channel update addressing the issue

Technical Details for CVE-2026-7977

Vulnerability Analysis

The vulnerability resides in the Canvas implementation within Chrome's rendering engine. The same-origin policy normally prevents JavaScript on one origin from reading pixel data or other content drawn from a different origin. An inappropriate implementation in Canvas allows a remote attacker to circumvent this boundary using a crafted HTML page.

The practical consequence is unauthorized cross-origin information access through the Canvas API. An attacker can render content from another origin and then extract data that should be protected by the browser's tainted-canvas restrictions. Exploitation requires the victim to load an attacker-controlled page, which is consistent with the user interaction requirement reflected in the CVSS metrics.

The issue is tracked publicly in the Chromium Issue Tracker Entry and resolved in the Google Chrome Stable Update.

Root Cause

The root cause is an improper enforcement of origin boundaries in Canvas operations. Canvas elements track an origin-clean flag that is cleared when cross-origin content is drawn, blocking subsequent pixel readback. The flawed code path fails to maintain this protection under specific conditions, classified under [CWE-269] as improper privilege management within the renderer's security model.

Attack Vector

Attack delivery occurs over the network through a crafted HTML page. A user must visit or be redirected to the attacker-controlled site, after which client-side JavaScript triggers the bypass. No authentication or elevated privileges are required. Successful exploitation yields limited disclosure of cross-origin resources rather than code execution.

No verified public proof-of-concept code is available. The vulnerability is described in prose because no sanitized exploitation example has been released by Google or Chromium maintainers.

Detection Methods for CVE-2026-7977

Indicators of Compromise

• Browser process telemetry showing outdated Chrome versions below 148.0.7778.96 connecting to untrusted domains
• Web proxy logs containing HTML responses with unusual Canvas API call sequences targeting cross-origin image or media resources
• Outbound POST requests carrying base64-encoded image payloads originating from browser sessions on suspicious pages

Detection Strategies

• Inventory installed Chrome builds across endpoints and flag any version preceding 148.0.7778.96
• Monitor user agent strings in web gateway logs to identify hosts running vulnerable Chrome versions
• Correlate visits to newly registered or low-reputation domains with Chrome versions known to be unpatched

Monitoring Recommendations

• Enable browser version reporting through enterprise management consoles such as Chrome Browser Cloud Management
• Apply web filtering and reputation-based blocking on egress traffic to reduce exposure to crafted HTML pages
• Centralize browser and proxy telemetry in a SIEM to correlate Chrome version data with browsing activity for triage

How to Mitigate CVE-2026-7977

Immediate Actions Required

• Update Google Chrome to version 148.0.7778.96 or later on all Windows, macOS, and Linux endpoints
• Restart Chrome after the update so the patched binaries are loaded into active browser sessions
• Audit Chromium-based browsers and embedded WebView components for upstream fix integration

Patch Information

Google published the fix in the May 2026 stable channel release for desktop. Administrators should consult the Google Chrome Stable Update advisory and deploy 148.0.7778.96 or later. Enterprise environments using managed update channels should verify rollout status through their browser management console.

Workarounds

• Restrict browsing to trusted sites using web filtering policies until patching is complete
• Disable JavaScript on untrusted origins through enterprise policy where business workflows permit
• Enforce Chrome auto-update policies to prevent users from delaying critical security updates

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

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

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