Skip to content
Fencer Vulns
high 8.3

CVE-2021-41263 json

Secure/signed cookies share secrets between sites in rails_multisite

published 2021-11-15 4 y ago modified 2026-07-08 4 mo ago also GHSA-844m-cpr9-jcmh , EUVD-2021-2317

cvss
8.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 50%
public exploits
0
none known

Summary

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.

Patch / fix

  • rubygems rails_multisite 4.0.0
  • discourse rails_multisite 4.0.0

Exploit prediction

0.63% chance of exploitation in the next 30 days, higher than 50% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H
NVD 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 6.0 AV:N/AC:M/Au:S/C:P/I:P/A:P
GitHub 3.1 6.2 CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:L/A:H

Affected packages

ecosystem package affected fixed in
rubygems rails_multisite
<4.0.0
4.0.0

Affected products

  • discourse rails_multisite

Classification

Weakness
  • CWE-200 Exposure of Sensitive Information to an Unauthorized Actor
  • CWE-565 Reliance on Cookies without Validation and Integrity Checking
  • CWE-327 Use of a Broken or Risky Cryptographic Algorithm

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.