CVE-2021-21288

Server-side request forgery in CarrierWave

Workarounds

Using proper network segmentation and applying the principle of least privilege to outbound connections from application servers can reduce the severity of SSRF vulnerabilities. Ideally the vulnerable gem should run on an isolated server without access to any internal network resources or cloud metadata access.

References

Server-Side Request Forgery Prevention Cheat Sheet

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 download feature has an SSRF vulnerability, allowing attacks to provide DNS entries or IP addresses that are intended for internal use and gather information about the Intranet infrastructure of the platform.

Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.

CVE-2021-21288 has a CVSS score of 4.3 (Medium). 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-2021-21288? CVE-2021-21288 is a medium-severity server-side request forgery (SSRF) vulnerability in carrierwave (rubygems), affecting versions < 1.3.2. It is fixed in 1.3.2, 2.1.1. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
2. How severe is CVE-2021-21288? CVE-2021-21288 has a CVSS score of 4.3 (Medium). 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-2021-21288? carrierwave (rubygems) versions < 1.3.2 is affected.
4. Is there a fix for CVE-2021-21288? Yes. CVE-2021-21288 is fixed in 1.3.2, 2.1.1. Upgrade to this version or later.
5. Is CVE-2021-21288 exploitable, and should I be worried? Whether CVE-2021-21288 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-2021-21288 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-2021-21288?
   • Upgrade carrierwave to 1.3.2 or later
   • Upgrade carrierwave to 2.1.1 or later

Other vulnerabilities in carrierwave