CVE-2026-11308: Chrome Extension Privilege Escalation Vulnerability

Technical summary

The vulnerability stems from an inappropriate implementation in Chrome's extension framework (CWE-269: Improper Control of the Ability to Choose Chosen Functionality). The extension permission model fails to properly enforce isolation boundaries, permitting a specially crafted extension to escalate its privileges beyond what the user granted during installation. While Google assigned this a Low severity rating internally (Chromium security), the CVSS 3.1 score of 6.3 (MEDIUM) reflects the practical risk: network-accessible attack vector, low complexity, no required privileges, and user interaction needed—but with integrity, confidentiality, and availability impact once the extension is installed.

Business impact

Organizations that allow Chrome usage face moderate risk. Compromised user machines could expose sensitive data, allow modification of local files, or disrupt operations depending on what the malicious extension does post-escalation. The threat is primarily to individual users and workstations rather than infrastructure, but in environments where Chrome is the primary browser or where users have administrative access, the impact amplifies. Supply chain risk also exists if attackers compromise legitimate extension developers or use deceptive extension listings to distribute malware.

Affected systems

Google Chrome versions prior to 149.0.7827.53 are affected across all major operating systems: Windows, macOS, and Linux. Any user running an older Chrome version who installs a malicious extension is at risk. The vulnerability does not affect Chrome on platforms where only official extensions from the Web Store are allowed, and enterprise deployments with extension blocklists or mandatory extension policies can significantly reduce exposure.

Exploitability

Exploitation requires user action—convincing someone to install a malicious extension—making it a medium-difficulty attack requiring social engineering. The attacker cannot exploit this remotely without user interaction, and the malicious extension must be delivered and installed first. However, once installed, the privilege escalation is deterministic and does not require further user interaction. Given the prevalence of social engineering and the difficulty many users have distinguishing legitimate from malicious extensions, this poses a realistic threat in targeted campaigns or widespread scams.

Remediation

The primary remediation is patching Chrome to version 149.0.7827.53 or later. Organizations should enforce automatic updates or deploy Chrome through managed channels. End users should update immediately via Settings > About Chrome, which typically triggers automatic installation. Additionally, implement extension policies to restrict installation to an approved allowlist, disable or remove suspicious extensions, and educate users on the risks of installing extensions from untrusted sources.

Patch guidance

Update Google Chrome to version 149.0.7827.53 or later. Most users will receive this automatically; verify the update by navigating to Chrome menu > About Google Chrome. For enterprise deployments, use Chrome policies to enforce updates via your management console. Verify the update has been applied by checking the browser version number—if it is 149.0.7827.53 or higher, the patch is installed. No interim workarounds eliminate the risk, so patching should be prioritized.

Detection guidance

Monitor for installations or updates of extensions from outside the Chrome Web Store, particularly those requesting broad permissions (host permissions to all sites, access to browsing data, etc.). Review browser extension audit logs if available in your endpoint detection and response (EDR) solution. Look for anomalous process spawning or privilege elevation events originating from the Chrome process or related chrome extensions processes. User training and reporting of suspicious extension installation prompts can surface early warning signs before exploitation occurs.

Why prioritize this

Although marked as Low severity by Chromium and not yet on CISA's Known Exploited Vulnerabilities (KEV) list, this warrants timely but not emergency-level action. The CVSS score of 6.3 reflects real risk: confidentiality and integrity impact with a user-interaction barrier that is not insurmountable for targeted attacks. Prioritize patching for high-risk users (those with admin rights, access to sensitive data) and Internet-facing machines, then roll out broadly. Organizations with mature extension management policies can deprioritize slightly but should still patch within your standard update cycle.

Risk score, explained

The CVSS 3.1 score of 6.3 (MEDIUM) balances several factors: the attack requires user interaction (UI:R, lowering severity), no special privileges are needed beforehand (PR:N), and the attack is network-accessible via social engineering (AV:N). However, impact is real—the vulnerability allows confidentiality (leaked data via the malicious extension), integrity (modified files or settings), and availability (crashed or disabled services) impact. The score appropriately reflects a practical mid-tier risk that should not be ignored but is less urgent than critical or high-severity flaws.

Frequently asked questions