CVE-2026-12454: Chrome macOS Safe Browsing Race Condition Enables Sandbox Escape

Technical summary

A race condition exists in the Safe Browsing implementation within Chromium prior to version 149.0.7827.155 on macOS (CWE-362). The vulnerability is triggered when a malicious renderer process—already running with reduced privileges inside Chrome's sandbox—races against Safe Browsing's security checks during HTML page processing. By exploiting timing gaps in the synchronization logic, an attacker can bypass sandbox restrictions and execute arbitrary code with the privileges of the Chrome process, potentially accessing system resources. The issue is specific to macOS and does not affect other platforms in the same way.

Business impact

For organizations deploying Chrome on macOS systems, this vulnerability represents a significant risk. While it requires an initial renderer compromise (typically through malicious content or a separate vulnerability), successful exploitation enables direct access to user data, credentials stored locally, and potential lateral movement into corporate networks. For businesses using macOS as their primary development or client platform, this could lead to intellectual property theft, credential compromise, or establishment of persistent backdoors. Unpatched systems remain vulnerable to coordinated multi-stage attacks combining web-based malware delivery with this sandbox escape.

Affected systems

This vulnerability affects Google Chrome versions prior to 149.0.7827.155 running on Apple macOS. Users on other operating systems (Windows, Linux, iOS, Android) are not affected by this specific race condition. However, organizations should verify their Chrome version and OS combination to confirm exposure, as macOS users represent a smaller but often high-value target set in enterprise environments.

Exploitability

Exploitation requires two prerequisites: (1) a compromised Chrome renderer process, and (2) user interaction to load a crafted HTML page. While these preconditions raise the barrier compared to a direct browser vulnerability, they are realistic in targeted attacks. An attacker might first deliver malware via phishing or watering hole attacks to compromise the renderer, then trigger the race condition with a follow-up payload. The race condition itself is not trivial to execute reliably, suggesting exploits require careful tuning. The vulnerability is not currently tracked in CISA's Known Exploited Vulnerabilities (KEV) catalog, indicating limited evidence of public weaponization at this time, but this does not diminish the strategic importance of patching.

Remediation

Users and administrators must upgrade Google Chrome to version 149.0.7827.155 or later on all macOS systems. Chrome's auto-update mechanism should distribute the patch automatically, but manual verification is recommended for critical systems. Additionally, consider supplementary mitigations: disable or restrict renderer access to high-risk content sources, enforce a macOS security policy that limits Chrome's system permissions, and segment development or high-value workstations from general network access to reduce the attack surface if a renderer compromise occurs.

Patch guidance

Apply Chrome version 149.0.7827.155 or later as soon as possible, prioritizing macOS devices in high-trust roles (developers, system administrators, executives). Verify patch deployment through Chrome's built-in update status (chrome://help) or mobile device management (MDM) tools for managed environments. For large fleets, stage deployment in lower-risk groups first to confirm compatibility. Note that the patch addresses only this race condition; users should maintain current Chrome versions to benefit from ongoing security fixes for the entire browser and its components.

Detection guidance

Detection of exploitation attempts is challenging because the attack occurs within the browser process after a renderer compromise. Monitor for: (1) unexpected child processes spawned by Chrome processes with elevated privileges; (2) Chrome process crashes or restarts coinciding with suspicious web activity; (3) access to sensitive local files or unusual network connections initiated from Chrome; (4) EDR telemetry showing sandbox policy violations tied to Chrome. Implement system-level monitoring of macOS sandbox escapes and correlate with Chrome process trees. Log and alert on attempts to load suspicious HTML pages that trigger Safe Browsing warnings followed by system-level activity.

Why prioritize this

This vulnerability deserves immediate attention because it combines high-severity impact (complete sandbox escape and system compromise), a plausible attack chain (renderer compromise + crafted content), and absence from the public KEV catalog suggesting defenders may underestimate its prevalence. While not zero-day and requiring prerequisite compromise, it is a critical privilege escalation path that significantly amplifies the damage of other browser-level exploits or social engineering attacks. Organizations relying on macOS should treat this as a priority patch.

Risk score, explained

The CVSS 3.1 score of 8.3 (High) reflects the combination of high confidentiality, integrity, and availability impact (C:H, I:H, A:H) balanced against moderate attack complexity (AC:H) and the requirement for user interaction (UI:R). The scope change (S:C) indicates that successful exploitation impacts resources beyond the vulnerable component (the browser sandbox). While the attack vector is network-based (AV:N), the precondition of an already-compromised renderer and race condition mechanics justify the elevated complexity score. This score appropriately signals a serious flaw requiring urgent patching without suggesting vulnerability to trivial exploitation.

Frequently asked questions