What is CVE-2021-41263?

CVE-2021-41263 is a medium-severity use of a broken or risky cryptographic algorithm vulnerability in rails_multisite (rubygems), affecting versions < 4.0.0. It is fixed in 4.0.0. The application uses a cryptographic algorithm known to have weaknesses, such as MD5, SHA-1, or DES.

How severe is CVE-2021-41263?

CVE-2021-41263 has a CVSS score of 6.2 (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.

Which versions of rails_multisite are affected by CVE-2021-41263?

rails_multisite (rubygems) versions < 4.0.0 is affected.

Is there a fix for CVE-2021-41263?

Yes. CVE-2021-41263 is fixed in 4.0.0. Upgrade to this version or later.

Is CVE-2021-41263 exploitable, and should I be worried?

Whether CVE-2021-41263 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.

What actually determines whether CVE-2021-41263 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.

How do I fix CVE-2021-41263?

Upgrade rails_multisite to 4.0.0 or later.

CVE-2021-41263 in rails_multisite

Q: How severe is CVE-2021-41263?

CVE-2021-41263 has a CVSS score of 6.2 (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.

Q: Which versions of rails_multisite are affected by CVE-2021-41263?

rails_multisite (rubygems) versions < 4.0.0 is affected.

Q: Is there a fix for CVE-2021-41263?

Yes. CVE-2021-41263 is fixed in 4.0.0. Upgrade to this version or later.

Q: Is CVE-2021-41263 exploitable, and should I be worried?

Whether CVE-2021-41263 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.

Q: What actually determines whether CVE-2021-41263 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.

Q: How do I fix CVE-2021-41263?

Upgrade rails_multisite to 4.0.0 or later.

Summary

Rails Multisite secure/signed cookies share secrets between sites in a multi-site application

Impact

This vulnerability impacts any Rails applications using rails_multisite alongside Rails' signed/encrypted cookies. Depending on how the application makes use of these cookies, it may be possible for an attacker to re-use cookies on different 'sites' within a multi-site Rails application.

The application uses a cryptographic algorithm known to have weaknesses, such as MD5, SHA-1, or DES. Typical impact: compromised confidentiality or integrity of protected data.

CVE-2021-41263 has a CVSS score of 6.2 (Medium). The vector is network-reachable, high 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 (4.0.0); upgrading removes the vulnerable code path.

Affected versions

rails_multisite (< 4.0.0)

Security releases

rails_multisite → 4.0.0 (rubygems)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

The issue has been patched in v4 of the rails_multisite gem. Note that this upgrade will invalidate all previous signed/encrypted cookies. The impact of this invalidation will vary based on the application architecture.

Frequently Asked Questions

What is CVE-2021-41263? CVE-2021-41263 is a medium-severity use of a broken or risky cryptographic algorithm vulnerability in rails_multisite (rubygems), affecting versions < 4.0.0. It is fixed in 4.0.0. The application uses a cryptographic algorithm known to have weaknesses, such as MD5, SHA-1, or DES.
How severe is CVE-2021-41263? CVE-2021-41263 has a CVSS score of 6.2 (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.
Which versions of rails_multisite are affected by CVE-2021-41263? rails_multisite (rubygems) versions < 4.0.0 is affected.
Is there a fix for CVE-2021-41263? Yes. CVE-2021-41263 is fixed in 4.0.0. Upgrade to this version or later.
Is CVE-2021-41263 exploitable, and should I be worried? Whether CVE-2021-41263 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
What actually determines whether CVE-2021-41263 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.
How do I fix CVE-2021-41263? Upgrade rails_multisite to 4.0.0 or later.