CVE-2025-5065: Google Chrome XSS Vulnerability

CVE-2025-5065 Overview

CVE-2025-5065 is a user interface (UI) spoofing vulnerability in the FileSystemAccess API of Google Chrome versions prior to 137.0.7151.55. A remote attacker can craft a malicious HTML page that manipulates the file system access prompts shown to users. This enables the attacker to deceive users into granting file or directory permissions they did not intend to provide. The flaw is classified under CWE-451: User Interface (UI) Misrepresentation of Critical Information. Google rated the issue as Medium severity in the Chromium security tracker. The vulnerability requires user interaction but no authentication, and exploitation occurs entirely over the network through a browser visit.

Critical Impact
A remote attacker can use a crafted web page to spoof Chrome's FileSystemAccess permission dialogs, potentially tricking users into exposing local files or directories.

Affected Products

Google Chrome versions prior to 137.0.7151.55 (Desktop)
Chromium-based browsers incorporating the affected FileSystemAccess API implementation
All operating system builds of Chrome Stable channel prior to the May 27, 2025 update

Discovery Timeline

2025-05-27 - CVE-2025-5065 published to NVD following the Chrome Stable channel update
2025-05-29 - Last updated in the NVD database

Technical Details for CVE-2025-5065

Vulnerability Analysis

The FileSystemAccess API allows web applications to read from and write to files and directories on the user's local system after the user grants permission through a browser dialog. The vulnerability stems from an inappropriate implementation in how Chrome renders and handles the associated UI elements. An attacker can craft an HTML page that manipulates the visual presentation of these permission prompts. The user sees a dialog that misrepresents the actual file or directory being requested, or obscures the scope of the access being granted. Because the prompt is the primary security boundary for the FileSystemAccess API, undermining its integrity directly weakens the consent model.

Root Cause

The root cause is a UI misrepresentation flaw [CWE-451] in the FileSystemAccess API surface. Chrome's permission flow did not adequately constrain the layout, focus, or content rendered around the file picker and permission prompts. This allowed attacker-controlled page content to influence what the user perceives during the consent step. The implementation gap is logic-level, not memory-related, so it produces no crash or measurable corruption.

Attack Vector

Exploitation requires a victim to visit an attacker-controlled or compromised website in a vulnerable Chrome build. The page triggers a FileSystemAccess request and surrounds it with overlay, framing, or timing tricks that misrepresent the prompt. If the user clicks through, the attacker site receives read or write handles to the chosen file or directory. The attack does not require credentials and operates fully over the network.

No verified public proof-of-concept code is available for CVE-2025-5065. Refer to the Chromium Issue Tracker Entry and the Google Chrome Update Blog for vendor-published details.

Detection Methods for CVE-2025-5065

Indicators of Compromise

Browser telemetry showing Chrome versions earlier than 137.0.7151.55 accessing untrusted websites
FileSystemAccess API grants to unfamiliar origins recorded in browser site settings or enterprise reporting
Unexpected reads or writes to user profile directories shortly after browser sessions on unknown domains

Detection Strategies

Inventory installed Chrome versions across managed endpoints and flag any build below 137.0.7151.55
Monitor Chrome Enterprise reporting for FileSystemAccess permission grants to non-corporate origins
Inspect proxy and DNS logs for outbound traffic to newly registered domains immediately preceding local file modifications

Monitoring Recommendations

Enable Chrome Enterprise Cloud Reporting to capture extension activity, version state, and site permission events
Forward endpoint browser telemetry and file integrity events into a centralized SIEM or data lake for correlation
Alert on first-time FileSystemAccess grants to external origins on user endpoints that handle sensitive data

How to Mitigate CVE-2025-5065

Immediate Actions Required

Update Google Chrome to version 137.0.7151.55 or later on all desktop platforms
Restart Chrome after applying the update so the patched binaries take effect
Audit existing FileSystemAccess permissions in chrome://settings/content/filesystem and revoke any unrecognized origins

Patch Information

Google addressed CVE-2025-5065 in the Chrome Stable channel update released on May 27, 2025, shipping fixed builds at version 137.0.7151.55 and later. Deployment details are documented in the Google Chrome Update Blog. Enterprises using managed Chrome should push the update through their existing distribution channels or enable automatic updates.

Workarounds

Disable the FileSystemAccess API via the DefaultFileSystemReadGuardSetting and DefaultFileSystemWriteGuardSetting enterprise policies until patching completes
Restrict FileSystemAccess to an allowlist of trusted internal origins using FileSystemReadAskForUrls and FileSystemWriteAskForUrls
Train users to verify the origin shown in Chrome's permission prompts before granting file or directory access

bash

# Example Chrome enterprise policy to block FileSystemAccess prompts until patched (Linux managed policy file)
cat <<'EOF' | sudo tee /etc/opt/chrome/policies/managed/filesystem_block.json
{
  "DefaultFileSystemReadGuardSetting": 2,
  "DefaultFileSystemWriteGuardSetting": 2
}
EOF