CVE-2021-21305

Code Injection vulnerability in CarrierWave::RMagick

Proof of Concept

class MyUploader < CarrierWave::Uploader::Base
  include CarrierWave::RMagick
end

MyUploader.new.manipulate!({ read: { density: "1 }; p 'Hacked'; {" }}) # => shows "Hacked"

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]

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)

Untrusted input is evaluated as executable code within the application's runtime environment. Typical impact: arbitrary code execution within the application's privilege context.

CVE-2021-21305 has a CVSS score of 7.4 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.3.2, 2.1.1); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

Upgrade to 2.1.1 or 1.3.2.

1. What is CVE-2021-21305? CVE-2021-21305 is a high-severity code injection vulnerability in carrierwave (rubygems), affecting versions < 1.3.2. It is fixed in 1.3.2, 2.1.1. Untrusted input is evaluated as executable code within the application's runtime environment.
2. How severe is CVE-2021-21305? CVE-2021-21305 has a CVSS score of 7.4 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of carrierwave are affected by CVE-2021-21305? carrierwave (rubygems) versions < 1.3.2 is affected.
4. Is there a fix for CVE-2021-21305? Yes. CVE-2021-21305 is fixed in 1.3.2, 2.1.1. Upgrade to this version or later.
5. Is CVE-2021-21305 exploitable, and should I be worried? Whether CVE-2021-21305 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2021-21305 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2021-21305?
   • Upgrade carrierwave to 1.3.2 or later
   • Upgrade carrierwave to 2.1.1 or later

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