CVE-2018-10895: Remote code execution due to CSRF in qutebrowser

Description

Due to a CSRF vulnerability affecting the qute://settings page, it was possible for websites to modify qutebrowser settings. Via settings like editor.command, this possibly allowed websites to execute arbitrary code.

This issue has been assigned CVE-2018-10895.

Affected versions

The issue was introduced in v1.0.0, as part of commit ffc29ee.

It was fixed in the v1.4.1 release, in commit 43e58ac.

All releases between v1.0.0 and v1.4.0 (inclusive) are affected. Backported patches are available, but no additional releases are planned:

(add .patch to the URL to get patches)

Timeline

2018-07-09: I was made aware of the original issue privately (initially believed by the reporter to only be a DoS issue), developed a fix and contacted the distros Openwall mailinglist to organize a disclosure date to give distributions time to coordinate releasing of a fix.

2018-07-10: Slightly updated patch sent to the distros mailinglist.

2018-07-11: Public disclosure.

Mitigation

Please upgrade to v1.4.1 or apply the patches above.

Note that disabling loading of autoconfig.yml is not a suitable remedy, since settings are still applied until the next restart.

As a workaround, it's possible to patch out the vulnerable code via a config.py file:

from qutebrowser.browser import qutescheme
qutescheme._qute_settings_set = lambda url: ('text/html', '')

While there is no known exploit for this in the wild, users are advised to check their autoconfig.yml file (located in the config folder shown in :version) for any unwanted modifications.

Credits

Thanks to:

  • toofar for reporting the initial issue.
  • Allan Sandfeld Jensen (carewolf) and Jüri Valdmann (juvaldma) of The Qt Company for their assistance with triaging and fixing the issue.
  • toofar and Jay Kamat (jgkamat) for reviewing the patch.
  • Morten Linderud (Foxboron) for suggestions on how to disclose this properly.

All posts

  1. qutebrowser v1.3.3 released (security update!)
  2. qutebrowser v1.2.0 released!
  3. qutebrowser v1.0.0 released!
  4. qutebrowser v0.10.0 released
  5. qutebrowser v0.8.0 released
  6. qutebrowser v0.7.0 released