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CVE-2021-33564: An argument injection vulnerability in the Dragonfly gem before 1.4.0 for Ruby allows remote attackers to r...

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.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2021-33564 affects Ruby applications using the Dragonfly gem before 1.4.0. If verify_url is disabled, a crafted URL can make image processing misuse ImageMagick convert arguments, allowing arbitrary file read or write. The CVE description says this may lead to code execution.

Executive priority

Treat as a high-priority remediation for internet-facing Ruby applications using Dragonfly. The business risk is unauthorized file access and possible code execution, but urgency depends on the vulnerable configuration being present.

Technical view

Dragonfly generate and process features mishandle arguments passed to ImageMagick convert. In versions before 1.4.0, with verify_url disabled, remote attackers may inject arguments through crafted URLs and cause arbitrary filesystem read/write. The provided sources do not include CVSS, CWE, or full vendor advisory detail.

Likely exposure

Most likely exposed systems are Ruby web applications using Dragonfly before 1.4.0, exposing Dragonfly URL-based processing to untrusted users, and running with verify_url disabled. Exposure is lower where Dragonfly is not used, upgraded, or not reachable by external users.

Exploitation context

The source bundle includes public issue, commit, comparison, research, nuclei template, and proof-of-concept references. CISA KEV is false, and the provided sources do not cite active exploitation in the wild.

Researcher notes

The key conditions are Dragonfly before 1.4.0, verify_url disabled, and reachable generate/process behavior using ImageMagick convert. Evidence supports public technical knowledge and detection material, but not confirmed active exploitation from the supplied sources.

Mitigation direction

  • Upgrade Dragonfly to version 1.4.0 or later.
  • Confirm verify_url is enabled wherever Dragonfly processing URLs are accepted.
  • Review vendor guidance and the fixing commit for configuration-specific requirements.
  • Limit Dragonfly processing routes to trusted callers where business logic permits.
  • Run the application with least filesystem privileges to reduce read/write impact.

Validation and detection

  • Inventory Ruby applications and Gemfile.lock entries for Dragonfly versions before 1.4.0.
  • Check application configuration for verify_url being disabled.
  • Identify public routes that invoke Dragonfly generate or process behavior.
  • Review logs for suspicious Dragonfly processing URLs or unexpected ImageMagick activity.
  • Confirm upgraded deployments use Dragonfly 1.4.0 or later.
Prepared
Confidence
medium
Sources
8

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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Execution behavior lookup

The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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CVE-2021-33564 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
7Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.