CVE-2021-41146: Arbitrary command execution on Windows in qutebrowser

First published: Thu Oct 21 2021(Updated: )

### Impact Starting with qutebrowser v1.7.0, the Windows installer for qutebrowser registers it as a handler for certain URL schemes. With some applications such as Outlook Desktop, opening a specially crafted URL can lead to argument injection, allowing execution of qutebrowser commands, which in turn allows arbitrary code execution via commands such as `:spawn` or `:debug-pyeval`. Only Windows installs where qutebrowser is registered as URL handler are affected. It does *not* have to be set as default browser for the exploit to work. ### Patches The issue has been fixed in [qutebrowser v2.4.0](https://github.com/qutebrowser/qutebrowser/releases/tag/v2.4.0) in commit 8f46ba3f6dc7b18375f7aa63c48a1fe461190430. The fix also adds additional hardening for potential similar issues on Linux (by adding the new `--untrusted-args` flag to the `.desktop` file), though no such vulnerabilities are known. Backported patches for older versions are available, but no further releases are planned: - v1.7.x: d1ceaab - v1.8.x: ca7155d - v1.9.x: 157d871 - v1.10.x: 94a6125 - v1.11.x: 10acfbb - v1.12.x: 363a18f - v1.13.x: 410f262 - v1.14.x: e4f4d93 - v2.0.x: 15a1654 - v2.1.x: 509ddf2 - v2.2.x: 03dcba5 - v2.3.x: 00a694c (commits are referring to qutebrowser/qutebrowser on GitHub) ### Workarounds Remove qutebrowser from the default browser settings entirely, so that it does not handle any kind of URLs. Make sure to remove *all* handlers, including an (accidental) `qutebrowserURL` handler, e.g. using [NirSoft URLProtocolView](https://www.nirsoft.net/utils/url_protocol_view.html). ### Timeline 2021-10-15: Issue reported via security@qutebrowser.org by Ping Fan (Zetta) Ke of [Valkyrie-X Security Research Group (VXRL)](https://www.vxrl.hk/) 2021-10-15: Issue confirmed by @The-Compiler (lead developer), author of installer (@bitraid) contacted for help/review 2021-10-15: CVE assigned by GitHub 2021-10-15 to 2021-10-17: Fix developed 2021-10-17: Additional core developer (@toofar) contacted for help/review 2021-10-21: v2.4.0 released containing the fix 2021-10-21: Advisory and fix published ### References See the [commit message](https://github.com/qutebrowser/qutebrowser/commit/8f46ba3f6dc7b18375f7aa63c48a1fe461190430) for additional information and references to various similar issues in other projects. ### Acknowledgements Thanks to Ping Fan (Zetta) Ke of [Valkyrie-X Security Research Group](https://www.vxrl.hk/) (VXRL/@vxresearch) for finding and responsibly disclosing this issue. ### Contact If you have any questions or comments about this advisory, please email [security@qutebrowser.org](mailto:security@qutebrowser.org).

Credit: security-advisories@github.com security-advisories@github.com

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