Introduction
An uninitialized variable in Google Chrome's Accessibility component on Windows can be used to escape the browser sandbox and turn a compromised renderer into a foothold on the underlying operating system. Chrome holds roughly 66.7 percent of the global browser market, so a sandbox escape at this layer has a large blast radius. Security teams managing Windows fleets should treat remediation as a priority.
Technical Information
The root cause of CVE-2026-6311 is classified as CWE-457: Use of Uninitialized Variable. The flaw is in Chrome's Accessibility component on Windows. When the affected code reads a variable that has not been properly initialized, the resulting value is undefined and typically contains residual data left on the stack by functions that ran earlier. An attacker who already has code execution in the renderer process can manipulate the stack so that the uninitialized variable holds attacker-controlled data. Pre-initializing stack memory through earlier actions is a well-documented exploitation pattern for bugs in the CWE-457 class, and it can lead to control-flow hijacking or arbitrary code execution.
The CVSS 3.1 vector for this vulnerability is AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H, which gives a base score of 8.3 (High). The "S:C" (Scope: Changed) designation confirms that successful exploitation breaks out of the vulnerable component's security boundary. In Chrome's architecture, that boundary is the sandbox.
Attack Flow
The exploitation chain has five stages:
- The attacker first gets code execution inside the sandboxed renderer process. This is a prerequisite, and it would typically take a separate vulnerability, such as a renderer memory corruption or remote code execution flaw.
- From inside the sandbox, the attacker crafts specific interactions with the Accessibility component on Windows, aimed at the code path that reads the uninitialized variable.
- The attacker grooms the stack. By arranging prior function calls or memory operations, they pre-populate the stack region where the uninitialized variable will be read and place controlled values in that memory.
- The Accessibility code reads the uninitialized variable and consumes the attacker-controlled data. Depending on how the variable is used, this can redirect execution flow or grant elevated privileges outside the sandbox.
- The attacker breaks out of Chrome's restricted environment and can affect the broader Windows system, with high impact to confidentiality, integrity, and availability.
The attack requires network access (the crafted HTML page must be served to the victim) and user interaction (the victim must visit or interact with the page). The high attack complexity rating reflects the need for an already compromised renderer process.
The Chromium issue tracker entry for this bug (issue 498201025) is currently restricted, so exploitation details and any internal patches are not yet public. Our analysis is based on the NVD description and the CWE-457 documentation.
Affected Systems and Versions
| Operating System | Vulnerability Status | Action Required |
|---|---|---|
| Windows | Affected: Google Chrome versions prior to 147.0.7727.101 | Update to 147.0.7727.101 or 147.0.7727.102 immediately |
| macOS | Not listed in CVE description | Maintain routine update cadence |
| Linux | Not listed in CVE description | Maintain routine update cadence |
The NVD description explicitly limits this vulnerability to Google Chrome on Windows. Security teams can patch Windows endpoints first and keep their standard update practices on other platforms.
Vendor Security History
Google runs a Vulnerability Rewards Program that pays for responsible disclosure of Chrome security issues. The reward tiers show the severity Google assigns to different vulnerability classes:
| Vulnerability Type | High-Quality Report Reward | Baseline Reward |
|---|---|---|
| Sandbox escape or memory corruption in a non-sandboxed process | Up to 250,000 USD | Up to 25,000 USD |
| Renderer RCE or memory corruption in a sandboxed process | Up to 55,000 USD | Up to 7,000 USD |
Google pays up to 250,000 USD for a sandbox escape report, which shows how seriously it treats this class of vulnerability. There is also a 1,000 USD bisect bonus for identifying the specific commit that introduced a bug.
Chrome still faces persistent pressure from threat actors despite these programs. On March 31, 2026, Google acknowledged that an exploit for CVE-2026-5281 existed in the wild, and zero-day exploitation of Chrome vulnerabilities remains an active concern.
References
- CVE-2026-6311 Detail, National Vulnerability Database
- Chrome Releases: Stable Channel Update for Desktop, April 15, 2026
- Chromium Issue 498201025 (restricted)
- CWE-457: Use of Uninitialized Variable
- Chrome Vulnerability Reward Program Rules
- Chrome Releases: Stable Channel Update for Desktop, March 31, 2026
- CVE-2026-6311 Summary, The Hacker Wire
- Browser Market Share Worldwide, StatCounter
