How severe is CVE-2021-21288?

CVE-2021-21288 has a CVSS score of 4.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-21288?

CVE-2021-21288 affects the following packages: carrierwave (RubyGems), carrierwave (RubyGems). Ecosystems affected: RubyGems.

How do I fix CVE-2021-21288?

Update carrierwave to 1.3.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21288 is resolved across your whole dependency graph.

How do I detect CVE-2021-21288 in my RubyGems dependencies?

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.

How do I mitigate CVE-2021-21288 if there is no patch (or I can't update yet)?

Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.

Is CVE-2021-21288 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-21288 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-21288?

CVE-2021-21288 has an EPSS (Exploit Prediction Scoring System) score of 1.2%, placing it in the 68th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-21288?

CVE-2021-21288 is classified as Server-Side Request Forgery (SSRF) (CWE-918). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2021-21288 published, and has it been updated?

CVE-2021-21288 was published on February 8, 2021 and was last updated on October 20, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

💎

💎 RubyGems

Not in CISA KEV

MEDIUM severity

CVE-2021-21288 — carrierwave

MEDIUMFix: carrierwaveuploader/carrierwave@012702e

CVE-2021-21288 is a medium-severity (CVSS 4.3) Server-Side Request Forgery (SSRF) vulnerability in carrierwave. A fix is available for carrierwave — see the affected versions and patch details below.

Server-side request forgery in CarrierWave

Also known asGHSA-fwcm-636p-68r5

Published

Feb 8, 2021

Updated

Oct 20, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Nov 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.2%probability of exploitation in next 30 days

Lower Risk+0.01%

Lower risk than most CVEs68th percentile — riskier than 68% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected

💎carrierwave💎carrierwave

Real-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 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.

Patches

Upgrade to 2.1.1 or 1.3.2.

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]

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
💎RubyGems	`carrierwave`	all versions	1.3.2`bundle update carrierwave --conservative`
💎RubyGems	`carrierwave`	≥ 2.0.0&&< 2.1.1	2.1.1`bundle update carrierwave --conservative`

Affected Products

1 product · 2 configurations

Application

carrierwavecarrierwave_project

≥ 2.0.1 && < 2.1.1

range

Detection & mitigation playbook

Open-source dependency

Detect
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-2021-21288 is resolved across your whole dependency graph.
Workarounds
Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.

Frequently Asked Questions

### Impact [CarrierWave download feature](https://github.com/carrierwaveuploader/carrierwave#uploading-files-from-a-remote-location) 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. ### Patches Upgrade to [2.1.1](https://rubygems.org/gems/carrierwave/versions/2.1.1) or [1.3.2](https://rubygems.org/gems/carrierwave/versions/1.3.2). ### Workarounds Using proper network segmentation and applying the principle of least privilege to outbound connections fr