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CVE-2021-33564

79
FAUCET Score

CVE-2021-33564 is a critical argument injection vulnerability in the Dragonfly gem for Ruby, affecting versions prior to 1.4.0. This flaw allows unauthenticated remote attackers to achieve arbitrary file read/write and potentially remote code execution by crafting malicious URLs when the verify_url option is disabled. With a CVSS score of 9.8 (Critical) and an EPSS score indicating high exploitability, the vulnerability poses a significant risk due to its network-based attack vector and low complexity. While there is no evidence of active exploitation or public Metasploit/ExploitDB modules, Nuclei templates exist for detecting and exploiting this RCE, and the lack of social media or media coverage is typical for most CVEs.

Impacted Technologies

VendorProductVersion(s)CPE
< 1.4.0CPE matchmatch criteria
cpe:2.3:a:dragonfly_project:dragonfly:*:*:*:*:*:ruby:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
72.25%
Probability of exploitation in next 30 days
EPSS Percentile
99.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
Nuclei: CVE-2021-33564 · May 29, 2021
This CVE's current EPSS score of 0.7225 is in the 98th percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

github_advisorypatch availablevia nvd_reference
View patch
rubygemspatch availablevia ghsa
Product: dragonflyFixed in: 1.4.0

Vendor Advisories (1)

rubygemsGHSA-j858-xp5v-f8xxcritical

Dragonfly contains remote code execution vulnerability

Jun 2, 2021

References

github.com / markevans/dragonfly/commit/25399297bb457f7fcf8e3f91e85945b255b111b5
PatchThird Party Advisory
github.com / markevans/dragonfly/compare/v1.3.0...v1.4.0
PatchThird Party Advisory
github.com / markevans/dragonfly/issues/513
Issue TrackingThird Party Advisory
github.com / mlr0p/CVE-2021-33564
ExploitThird Party Advisory
raw.githubusercontent.com / projectdiscovery/nuclei-templates/master/cves/2021/CVE-2021-33564.yaml
ExploitThird Party Advisory
zxsecurity.co.nz / research/argunment-injection-ruby-dragonfly
ExploitThird Party Advisory