CVE-2021-41263

Name: CVE-2021-41263
Creator: NVD / NIST
Published: 2021-11-15T20:15:20.037+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.8/10EPSS 0.61%

Last modified Jun 17, 2026

CVE-2021-41263 is a high-severity vulnerability rated 8.8/10 on the CVSS scale. rails_multisite provides multi-db support for Rails applications. In affected versions this vulnerability impacts any Rails applications using `rails_multisite` alongside Rails' signed/encrypted cookies. EPSS estimates a 0.61% chance of exploitation in the next 30 days.

Description

rails_multisite provides multi-db support for Rails applications. In affected versions 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 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.

Metrics

CVSS 3.1

8.8/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

0.61%

44.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Discourse	Rails Multisite	< 4.0.0

References

https://github.com/discourse/rails_multisite/commit/c6785cdb5c9277dd2c5ac8d55180dd1ece440ed0Patch, Third Party Advisory
https://github.com/discourse/rails_multisite/security/advisories/GHSA-844m-cpr9-jcmhThird Party Advisory
https://github.com/discourse/rails_multisite/commit/c6785cdb5c9277dd2c5ac8d55180dd1ece440ed0Patch, Third Party Advisory
https://github.com/discourse/rails_multisite/security/advisories/GHSA-844m-cpr9-jcmhThird Party Advisory

Timeline

Published: Nov 15, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-41263?

How severe is CVE-2021-41263?

CVE-2021-41263 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 0.61% probability of exploitation in the next 30 days.

How do I fix CVE-2021-41263?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-41263?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST