CVE-2021-41263
Secure/signed cookies share secrets between sites in rails_multisite
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- Low
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Secure/signed cookies share secrets between sites in rails_multisite
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.
- Record
CVE-2021-41263- CVSS 3.1
- 8.3 High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H - Weakness
- CWE-200, CWE-565
- Updated
- 2026-11-02
EUVDEUVD-2021-2317
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.
- Record
EUVD-2021-2317- CVSS 3.1
- 8.3 High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-844m-cpr9-jcmh
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.
Patches
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.
- Record
GHSA-844m-cpr9-jcmh- CVSS 3.1
- 6.2 Medium
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:L/A:H - Weakness
- CWE-200, CWE-327, CWE-565
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2021-41263- CVSS 3.1
- 8.3 High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H - CVSS 3.1
- 8.8 High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - CVSS 2.0
- 6.0 Medium
AV:N/AC:M/Au:S/C:P/I:P/A:P - Weakness
- CWE-200, CWE-565, CWE-327
- Updated
- 2026-11-02
OSV
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.
- Record
CVE-2021-41263- CVSS 3.1
- 8.8 High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSVGHSA-844m-cpr9-jcmh
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.
Patches
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.
- Record
GHSA-844m-cpr9-jcmh- CVSS 3.1
- 6.2 Medium
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:L/A:H - Weakness
- CWE-200, CWE-327, CWE-565
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
rails_multisiteRubyGems |
before 4.0.0 | 4.0.0 |
rails_multisiteRubyGems |
before 4.0.0, plus listed versions 0.0.11.0.11.0.21.0.31.0.4 Show 23 moreShow less1.0.51.0.61.1.01.1.0.rc11.1.0.rc21.1.0.rc31.1.0.rc41.1.11.1.22.0.12.0.22.0.42.0.62.0.72.1.02.1.12.1.22.2.22.3.02.4.02.5.03.0.03.1.0 |
4.0.0 |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-41263 is a high vulnerability (CVSS 8.3) in Discourse Rails Multisite, published November 15, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.63%, the 50th percentile. Fixed in rails_multisite 4.0.0.
References
github.com/discourse/rails_multisite/security/advisories/GHSA-844m-cpr9-jcmh
nvd.nist.gov/vuln/detail/CVE-2021-41263