CVE-2021-21305 is a high-severity (CVSS 8.8) CWE-74 vulnerability in carrierwave. 1 public exploit reference exists, so weaponization risk is real. A fix is available for carrierwave — see the affected versions and patch details below.
Code Injection vulnerability in CarrierWave::RMagick
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2021-21305 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the 10–50% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
carrierwave💎carrierwaveReal-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
Impact
CarrierWave::RMagick has a Code Injection vulnerability. Its #manipulate! method inappropriately evals the content of mutation option(:read/:write), allowing attackers to craft a string that can be executed as a Ruby code.
If an application developer supplies untrusted inputs to the option, it will lead to remote code execution(RCE).
(But supplying untrusted input to the option itself is dangerous even in absence of this vulnerability, since is prone to DoS vulnerability - attackers can try to consume massive amounts of memory by resizing to a very large dimension)
Proof of Concept
class MyUploader < CarrierWave::Uploader::Base
include CarrierWave::RMagick
end
MyUploader.new.manipulate!({ read: { density: "1 }; p 'Hacked'; {" }}) # => shows "Hacked"
Patches
Workarounds
Stop supplying untrusted input to #manipulate!'s mutation option.
References
Code Injection Software Attack
For more information
If you have any questions or comments about this advisory:
- Open an issue in CarrierWave repo
- Email me at [email protected]
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | carrierwave | all versions | 1.3.2bundle update carrierwave --conservative |
| 💎RubyGems | carrierwave | ≥ 2.0.0&&< 2.1.1 | 2.1.1bundle update carrierwave --conservative |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for carrierwave, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update carrierwave to 1.3.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21305 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 O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2021-21305 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-21305. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Frequently Asked Questions
Is CVE-2021-21305 in your dependencies?
O3 Security finds CVE-2021-21305 across RubyGems dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.