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

Advisory record · `GHSA-844m-cpr9-jcmh`

- **Identifiers:** `GHSA-844m-cpr9-jcmh` · `CVE-2021-41263`
- **State:** Confirmed
- **Severity:** CVSS 8.3 High
- **Critical:** No
- **Weakness (CWE):** [CWE-200](https://cwe.mitre.org/data/definitions/200.html) · [CWE-327](https://cwe.mitre.org/data/definitions/327.html) · [CWE-565](https://cwe.mitre.org/data/definitions/565.html)
- **Tags:** [Information disclosure](https://agentprime.io/advisories/tag/info-disclosure.md) · [Weak cryptography or TLS](https://agentprime.io/advisories/tag/weak-crypto.md) · [CWE-565](https://agentprime.io/advisories/tag/cwe-565.md)
- **Published:** 15 Nov 2021
- **Updated:** 8 Jul 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 15 Nov 2021, 17:54 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `rails_multisite` (RubyGems): affected `<4.0.0`; fixed in `4.0.0`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 8.3 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0063, the 50th percentile, on 6 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the GitHub Advisory Database, published 15 Nov 2021. New records show when each source confirmed them.

## Sources

- [GitHub Advisory Database: GHSA-844m-cpr9-jcmh](https://github.com/advisories/GHSA-844m-cpr9-jcmh)
- [OSV: GHSA-844m-cpr9-jcmh](https://osv.dev/vulnerability/GHSA-844m-cpr9-jcmh)
- <https://github.com/discourse/rails_multisite/security/advisories/GHSA-844m-cpr9-jcmh>
- <https://nvd.nist.gov/vuln/detail/CVE-2021-41263>
- <https://github.com/discourse/rails_multisite/commit/c6785cdb5c9277dd2c5ac8d55180dd1ece440ed0>
- <https://github.com/discourse/rails_multisite>
- <https://github.com/rubysec/ruby-advisory-db/blob/master/gems/rails_multisite/CVE-2021-41263.yml>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-844m-cpr9-jcmh>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-844m-cpr9-jcmh/>. Everything for agents: <https://agentprime.io/llms.txt>.