Google Chrome Sandbox Escape via Uninitialized Use in Accessibility (CVE-2026-6311)

CVE-2026-6311 describes a high-severity vulnerability affecting Google Chrome on Windows. Specifically, an uninitialized use in the Accessibility component exists in versions prior to 147.0.7727.101. This flaw allows a remote attacker, who has already compromised the renderer process, to potentially escape the browser’s sandbox environment. The attacker exploits this vulnerability by crafting a malicious HTML page. Successful exploitation allows the attacker to execute code outside of the Chrome sandbox, potentially leading to arbitrary code execution on the underlying system. This vulnerability was patched in Chrome version 147.0.7727.101, released in April 2026. The Chromium project assigned a security severity of High to this issue.

Attack Chain

1. The attacker crafts a malicious HTML page designed to trigger the uninitialized use vulnerability in the Accessibility component.
2. The victim visits the malicious HTML page through a phishing link or drive-by download.
3. The HTML page is rendered by Google Chrome, which triggers the vulnerability in the Accessibility component.
4. Due to the uninitialized memory, the attacker gains control of a pointer or other sensitive data.
5. The attacker leverages this control to read from or write to arbitrary memory locations within the renderer process.
6. The attacker manipulates the memory of the renderer process to bypass sandbox restrictions.
7. The attacker gains the ability to execute arbitrary code outside of the Chrome sandbox.
8. The attacker can now perform actions such as installing malware, stealing sensitive data, or pivoting to other systems on the network.

Impact

Successful exploitation of CVE-2026-6311 allows an attacker to escape the Google Chrome sandbox on Windows systems. This can lead to arbitrary code execution on the victim’s machine, potentially leading to data theft, malware installation, or further compromise of the network. Given Chrome’s widespread use, this vulnerability poses a significant risk to a large number of users. While the exact number of victims is unknown, the potential impact is high due to the ability to bypass the browser’s security measures.

Recommendation

• Upgrade Google Chrome to version 147.0.7727.101 or later to patch CVE-2026-6311 (reference: Overview).
• Monitor process creation events for unexpected processes spawned by Chrome renderer processes, as a sign of successful sandbox escape (reference: Attack Chain step 8 and the “Detect Chrome Sandbox Escape via Child Process” Sigma rule).
• Implement web filtering to block access to known malicious websites that may host exploit code targeting this vulnerability (reference: Attack Chain step 2).
• Deploy the Sigma rules in this brief to your SIEM and tune for your environment.