CVE-2026-11656: Chrome ServiceWorker Use-After-Free Sandbox Escape Vulnerability

Technical summary

CVE-2026-11656 is a use-after-free memory safety vulnerability (CWE-416) in the ServiceWorker implementation within Chromium's rendering engine. When a specially crafted Chrome extension manipulates ServiceWorker lifecycle events, it can cause the browser to reference memory that has already been freed, leading to code execution with privileges sufficient to bypass the sandbox isolation layer. The vulnerability is reachable only through extension installation, which requires user consent, but once triggered, the attacker gains access to system resources normally protected by the security model.

Business impact

Organizations relying on Chrome for business operations face risk if users can be socially engineered into installing malicious extensions. A successful exploit enables attackers to access sensitive data stored on the system, execute arbitrary code with user privileges, and potentially pivot to other systems on the network. The impact is especially severe in environments where Chrome is the primary browser for SaaS applications, remote work, or secure data handling. Remediation requires both patching Chrome and reviewing installed extensions across the user base.

Affected systems

Google Chrome versions prior to 149.0.7827.103 on all supported platforms are affected. While the CVE lists multiple operating systems (Windows, macOS, and Linux), the vulnerability is in the Chrome browser itself; the OS is affected only as the host for the vulnerable browser. Organizations should prioritize patching Chrome across all endpoints regardless of OS platform.

Exploitability

Exploitation requires two conditions: (1) a user must be convinced to install a malicious Chrome extension, and (2) the extension must trigger the use-after-free condition during ServiceWorker operation. While the technical barrier to crafting the exploit is moderate, the social engineering requirement is the primary gating factor. The vulnerability has not been publicly disclosed as actively exploited in the wild as of the publication date, but the sandbox escape potential makes it a high-value target for adversaries. No exploitation is currently tracked in public vulnerability databases.

Remediation

Update Google Chrome to version 149.0.7827.103 or later on all systems. Verify the update through Chrome's Settings > About > Google Chrome menu, which automatically checks for and installs updates. Additionally, audit installed extensions organization-wide using Chrome's extension management console or mobile device management (MDM) solutions to identify and remove any suspicious or unverified extensions. End-user security training should emphasize the risks of installing extensions from untrusted sources.

Patch guidance

Chrome auto-updates by default; however, users should manually verify they are running version 149.0.7827.103 or later in Settings > About > Google Chrome. Enterprise administrators should use Chrome policies (such as "ExtensionInstallWhitelist" and "ExtensionInstallBlacklist") to restrict which extensions users can install. MDM solutions can enforce automatic updates and restrict extension permissions. For organizations with slower update cycles, consider implementing policies that block installation of extensions from the Chrome Web Store until a patch verification period has elapsed.

Detection guidance

Monitor Chrome extension installations across your organization using MDM solutions or Chrome Enterprise reporting features. Look for recently installed extensions from developers with low or no reputation, or extensions with unusually broad permissions (especially those requesting access to sensitive APIs). Endpoint Detection and Response (EDR) tools may flag suspicious process creation or memory access patterns from Chrome child processes. Review audit logs for ServiceWorker-related crashes or unexpected process terminations, which may indicate failed exploitation attempts. Inspect Chrome Extension Reporting events in Windows Event Logs (if available) for installations that deviate from organizational policy.

Why prioritize this

Assign high priority due to the combination of a high CVSS score (8.3), sandbox escape capability, and the ubiquity of Chrome in enterprise environments. Although exploitation requires user interaction, the consequence—code execution outside the sandbox—is severe. The lack of public active exploitation provides a window to patch before the vulnerability becomes widely weaponized. Organizations with heavy Chrome usage, remote workforces, or strict data handling requirements should treat this as critical.

Risk score, explained

The CVSS 3.1 score of 8.3 (HIGH) reflects: Network-based attack vector (AV:N) because the malicious extension can be delivered via the internet; High complexity (AC:H) due to the requirement to craft a specific trigger within an extension; No privileges required (PR:N) but User interaction required (UI:R) since users must install the extension; Scope changed (S:C) because the sandbox boundary is crossed; and High impact on Confidentiality, Integrity, and Availability (C:H/I:H/A:H) as the attacker gains system-level code execution. The score appropriately weights the sandbox escape impact against the user interaction requirement.

Frequently asked questions