CVE-2026-12437: Google Chrome Use-After-Free Vulnerability

CVE-2026-12437 Overview

CVE-2026-12437 is a use-after-free vulnerability [CWE-416] in the WebShare component of Google Chrome on Windows. The flaw affects Chrome versions prior to 149.0.7827.155. An attacker who has already compromised the renderer process can leverage a crafted HTML page to potentially escape the Chrome sandbox. Google's Chromium security team rated the underlying issue as Critical severity, while the National Vulnerability Database lists it as HIGH with a CVSS score of 8.3.

Critical Impact
Successful exploitation enables a sandbox escape from a compromised renderer process, allowing code execution at the broader browser privilege level on Windows hosts.

Affected Products

Google Chrome on Windows prior to 149.0.7827.155
Microsoft Windows hosts running vulnerable Chrome builds
Chromium-based downstream browsers that share the WebShare implementation

Discovery Timeline

2026-06-17 - CVE-2026-12437 published to NVD
2026-06-18 - Last updated in NVD database

Technical Details for CVE-2026-12437

Vulnerability Analysis

The vulnerability resides in the WebShare implementation in Chrome on Windows. WebShare exposes the navigator.share() Web API, which lets pages invoke the native Windows share UI. The defect is a use-after-free in objects managed by this component. An attacker with renderer compromise can manipulate WebShare object lifetimes from a crafted HTML page. When the freed memory is reused through a controlled allocation, the attacker gains read or write access to attacker-influenced data structures. This primitive, chained with renderer-side control, can be used to break out of the Chrome sandbox into the browser process context. Exploitation requires user interaction and a prior renderer compromise, which is reflected in the attack complexity rating.

Root Cause

The root cause is improper object lifetime management in the WebShare code path. A reference to a WebShare-related object is retained or dereferenced after the object has been freed. Concurrent or sequential JavaScript operations can trigger destruction of the object while a pending operation still holds a dangling pointer. Reuse of the stale pointer yields the classic use-after-free condition tracked under [CWE-416].

Attack Vector

Exploitation requires the attacker to have first compromised the renderer process, typically via a separate renderer-side bug. The attacker then serves a crafted HTML page that calls into the WebShare API in a sequence designed to free and reallocate the target object. User interaction is required to trigger the share flow on Windows. Once the dangling pointer is reused, the attacker pivots from the sandboxed renderer to higher-privileged browser process code, achieving a sandbox escape.

No public proof-of-concept is currently available, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. See the Chromium Issue Tracker Entry for upstream technical context.

Detection Methods for CVE-2026-12437

Indicators of Compromise

Chrome browser processes spawning unexpected child processes on Windows endpoints running builds older than 149.0.7827.155
Crash reports from chrome.exe referencing the WebShare or sharing service code paths
Outbound connections from renderer processes to attacker-controlled domains hosting HTML pages that invoke navigator.share()

Detection Strategies

Inventory Chrome versions across managed Windows endpoints and flag any build below 149.0.7827.155
Hunt for browser process tree anomalies where chrome.exe renderer or utility processes launch shells, scripting engines, or LOLBins
Correlate Chrome crash telemetry with navigation events to identify repeated faults in WebShare-adjacent modules

Monitoring Recommendations

Forward Chrome process telemetry, command lines, and crash events into a centralized data lake for retrospective hunting
Monitor Windows endpoint logs for unexpected memory access violations originating from Chrome processes
Track third-party Chromium-based browsers in the environment and align their patch state to the Chrome 149 baseline

How to Mitigate CVE-2026-12437

Immediate Actions Required

Update Google Chrome on all Windows endpoints to version 149.0.7827.155 or later
Force-restart Chrome after deployment so the patched binary is loaded into memory
Audit any Chromium-based browsers in the estate and apply the corresponding upstream fix

Patch Information

Google addressed the issue in the Stable channel update for desktop. Administrators should consult the Google Chrome Stable Update advisory for the full set of fixes shipped alongside CVE-2026-12437. Enterprise deployments managed through Group Policy or Chrome Browser Cloud Management should validate that the TargetVersionPrefix and update server policies allow clients to reach 149.0.7827.155.

Workarounds

Restrict use of Chrome on Windows hosts that cannot be promptly patched and route users to a patched browser
Disable or block access to untrusted sites that invoke navigator.share() via web filtering until the patch is deployed
Apply application allowlisting to prevent unexpected child processes from spawning under chrome.exe

bash

# Verify Chrome version on a Windows endpoint
reg query "HKLM\Software\Google\Update\Clients\{8A69D345-D564-463C-AFF1-A69D9E530F96}" /v pv

# Enforce minimum version via Chrome Enterprise policy (registry)
reg add "HKLM\Software\Policies\Google\Update" /v TargetVersionPrefix /t REG_SZ /d "149.0.7827.155" /f