CVE-2021-33564 is a critical-severity (CVSS 9.8) CWE-88 vulnerability in dragonfly. 7 public exploit or proof-of-concept references are indexed, so weaponization risk is real. A fix is available for dragonfly — see the affected versions and patch details below.
Dragonfly contains remote code execution vulnerability
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
dragonflyReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
An argument injection vulnerability in the Dragonfly gem before 1.4.0 for Ruby allows remote attackers to read and write to arbitrary files via a crafted URL when the verify_url option is disabled. This may lead to code execution. The problem occurs because the generate and process features mishandle use of the ImageMagick convert utility.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | dragonfly | all versions | 1.4.0bundle update dragonfly --conservative |
Affected Products
dragonflydragonfly_projectResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
An argument injection vulnerability in the Dragonfly gem before 1.4.0 fo…
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Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for dragonfly, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update dragonfly to 1.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-33564 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How to detect CVE-2021-33564
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2021-33564 -u https://target- Template
- Ruby Dragonfly <1.4.0 - Remote Code Execution
- Severity
- critical
- Impact
- Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code on the affected system.
- Remediation
- Upgrade Ruby Dragonfly to version 1.4.0 or later to mitigate this vulnerability.
Template by ProjectDiscovery nuclei-templates (0xsapra), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2021-33564 in your dependencies?
Find it across RubyGems, including transitive dependencies.