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HIGH severity

Arbitrary command execution on Windows via qutebrowserurl: URL handlerGHSA-vw27-fwjf-5qxm

HIGHFix: qutebrowser/qutebrowser@8f46ba3

GHSA-vw27-fwjf-5qxm is a high-severity (CVSS 8.8) CWE-77 vulnerability in qutebrowser. A fix is available for qutebrowser — see the affected versions and patch details below.

Also known asCVE-2021-41146PYSEC-2021-382
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.5%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs73th percentile — riskier than 73% of all scored CVEsHighest risk
0.24%0.83%1.41%2.00%0.7%1.5%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-vw27-fwjf-5qxm by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 384,534 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
🐍qutebrowser

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

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 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.

Timeline

2021-10-15: Issue reported via [email protected] by Ping Fan (Zetta) Ke of Valkyrie-X Security Research Group (VXRL) 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 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 (VXRL/@vxresearch) for finding and responsibly disclosing this issue.

Contact

If you have any questions or comments about this advisory, please email [email protected].

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPIqutebrowser≥ 1.7.0&&< 2.4.02.4.0pip install --upgrade 'qutebrowser==2.4.0'

Affected Products

1 product · 2 configurations
Application
qutebrowserqutebrowser
≥ 2.0.0 && ≤ 1.7.0
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for qutebrowser, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update qutebrowser to 2.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-vw27-fwjf-5qxm is resolved across your whole dependency graph.

  3. Workarounds

    Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.

Frequently Asked Questions

### 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.
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