Introduction
A critical Use After Free in Google Chrome's Proxy component can let an attacker with a privileged network position escape the browser sandbox. What should be an isolated rendering context becomes a foothold on the underlying system. Chrome held roughly 66.7 percent of the global desktop browser market as of March 2026, so a very large number of endpoints are exposed to CVE-2026-6297. That makes this one of the more consequential fixes in the April 2026 Stable channel update.
Technical Information
Root Cause: Use After Free in the Proxy Subsystem
CVE-2026-6297 is classified under CWE-416 (Use After Free). This class of vulnerability occurs when a program keeps referencing memory after that memory has been freed. Depending on the state of the heap at the time of the dangling dereference, exploitation can cause a crash, produce unexpected values, or give an attacker arbitrary code execution.
The vulnerable component is Chrome's Proxy subsystem. Based on the architecture of Chromium's networking stack, the affected code path likely resides under net/proxy_resolution/ or services/network/. In this scenario, a proxy-related object is freed during normal processing, but a pointer to that object persists and is later dereferenced. If an attacker can influence the contents of the freed memory region (for example, through heap spraying triggered by the crafted HTML page), they can redirect execution flow.
Why Sandbox Escape Matters
The NVD description states that this vulnerability enables a sandbox escape. Chrome's multi-process architecture uses a sandbox to isolate the renderer process from the rest of the system. For a Use After Free in the Proxy component to cross that boundary, the freed object's code path must span the interface between the renderer process and the browser process (or the network service process). That crossing is what lifts the severity from a typical renderer bug to a critical finding.
CISA-ADP assigned a CVSS v3.1 vector of AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H, which gives a score of 8.3 HIGH. The S:C (Scope: Changed) component reflects the sandbox escape, because the vulnerability's impact extends beyond the security scope of the vulnerable component.
Attack Flow
- The attacker must occupy a privileged network position. That could mean running a malicious Wi-Fi access point, performing ARP spoofing on a local network, or controlling an upstream proxy server.
- From that position, the attacker can influence or inject proxy-related responses that Chrome's networking layer processes.
- The attacker serves the victim a crafted HTML page, or redirects the victim to one. The page triggers the code path in the Proxy component where the Use After Free condition exists.
- Chrome dereferences the freed proxy object. If the attacker has arranged for controlled data to occupy the freed memory (via heap manipulation techniques embedded in the HTML payload), they gain control of execution.
- Because the vulnerable code path crosses the renderer/browser process boundary, successful exploitation breaks out of Chrome's sandbox and may allow code execution with the privileges of the browser process.
Context: A Dense Cluster of Critical Fixes
The April 15, 2026 release included 31 security fixes. Five were rated Critical, CVE-2026-6297 among them:
| CVE ID | Component | Vulnerability Type | Reporter | Bounty |
|---|---|---|---|---|
| CVE-2026-6296 | ANGLE | Heap buffer overflow | cinzinga | $90,000 |
| CVE-2026-6297 | Proxy | Use after free | heapracer | $10,000 |
| CVE-2026-6298 | Skia | Heap buffer overflow | 86ac1f1587b71893ed2ad792cd7dde32 | TBD |
| CVE-2026-6299 | Prerender | Use after free | N/A | |
| CVE-2026-6358 | XR | Use after free | Jihyeon Jeong | TBD |
All five Critical fixes are memory safety bugs, and they span five different components. Two are heap buffer overflows (ANGLE and Skia), and three are Use After Free bugs (Proxy, Prerender, and XR).
Patch Information
Google fixed CVE-2026-6297 in the Chrome Stable channel update released on April 15, 2026, which brought the browser to version 147.0.7727.101 for Linux and 147.0.7727.101/102 for Windows and macOS. The fix shipped as a point release on the existing Chrome 147 branch (branch-heads/7727) rather than in a full milestone release, which signals how urgently the Chromium team treated this flaw.
The Chromium issue tracker lists the vulnerability as issue 493628982. As is standard practice for Chromium security bugs of this severity, access to the entry remains restricted while the patch propagates globally, to prevent exploitation.
The Chromium source repository's git log between tags 147.0.7727.100 and 147.0.7727.101 shows several cherry-picked security fixes in this release. Multiple UAF fixes were cherry-picked into the build, including fixes for ServiceWorkerContextCore and FileSystemAccessChangeSource, but no explicitly labeled commit message corresponds to the Proxy component fix for CVE-2026-6297. That is consistent with how the Chromium project handles its most sensitive security fixes. They often reach the release branch through batched "Roll commits from side projects" merges, which deliberately obscure the exact change and limit the window for adversaries to reverse engineer it. Two such roll commits, 483802f and 707f814, appear in this release's log.
Chrome updates itself, so most consumer users will receive this patch without doing anything. Users and administrators can confirm they are protected by checking that their Chrome version is 147.0.7727.101 or later via chrome://settings/help. Chromium-based browsers that consume the upstream Chromium codebase (e.g., Microsoft Edge, Brave, Opera) will need to integrate these fixes from the 7727 branch independently.
Because the attack vector requires a privileged network position, organizations should patch devices that often connect to untrusted or public networks first. No vendor workarounds or alternative mitigations have been published. Patching remains the only confirmed remediation.
Affected Systems and Versions
The following versions and configurations are affected:
- Google Chrome for Linux: All versions prior to 147.0.7727.101
- Google Chrome for Windows: All versions prior to 147.0.7727.101/102
- Google Chrome for macOS: All versions prior to 147.0.7727.101/102
- Chromium-based browsers (Microsoft Edge, Brave, Opera, and others): Any builds that have not yet integrated the fix from the
branch-heads/7727branch are potentially vulnerable
The vulnerability is exploitable when a user on an affected version visits a crafted HTML page while an attacker occupies a privileged network position.
Vendor Security History
The April 15, 2026 release that fixed CVE-2026-6297 included 31 security fixes in total, five of them rated Critical. That many critical memory safety bugs in a single release is notable. Google's Vulnerability Rewards Program remains a major driver of external security research on Chrome. For this vulnerability, Google awarded $10,000 to the researcher "heapracer", who reported the issue on March 17, 2026. For comparison, CVE-2026-6296 (a heap buffer overflow in ANGLE reported in the same release cycle) earned a $90,000 bounty, one of the larger Chrome VRP payouts we have seen.
Google uses a SecurityEmbargo hotlist to keep highly sensitive bugs restricted indefinitely, so that embedders and users have time to patch before technical details become public. The restricted status of issue 493628982 reflects this practice.
