PatchTheCVECVE-2021-33564: An argument injection vulnerability in the Dragonfly gem before 1.4.0 for Ruby allows remote attackers to read
CVE-2021-33564 is a critical-severity flaw (CVSS 9.8) affecting dragonfly. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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.
Why this priority
- Critical severity
- EPSS top 1%: very likely to be exploited
- Public exploit reference
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 9.8 (Critical) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 72.1% (top 1%) |
| CISA exploited list | No |
| Weakness | CWE-88 |
| Published | 2021-05-29 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Public exploits and detection
Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.
- Nuclei scan template: Ruby Dragonfly <1.4.0 - Remote Code Execution
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2021-33564?
dragonfly: upgrade to 1.4.0. Exact commands for each OS are on this page.
Is CVE-2021-33564 being exploited?
CVE-2021-33564 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2021-33564 affect?
CVE-2021-33564 affects dragonfly. Severity is critical (CVSS 9.8). 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 probl
How urgent is CVE-2021-33564?
Priority 69/100. Critical severity; EPSS top 1%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action
Software pages
Ruby vulnerabilities · ImageMagick vulnerabilities
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