CVE-2021-41263

HIGHNVD 8.38.3—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.3 under NVD CVSS v3. EPSS exploit probability: 0.6% (48th percentile of EPSS-scored CVEs). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
8.3EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.6%CVSS: 8.3Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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.

CVSS v3
8.3
EG Score
8.3HIGHmedium confidence
EG Risk
42
EG Risk 42/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity83% × 45%
Exploitation1% × 40%
Automatability30% × 15%
CISA SSVC: Track at low or medium mission impact; Track or Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.6%
EPSS %ILE
48th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track or Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (no KEV listing, exploit record or EPSS ≥ 50%) · Automatable unknown (not published for this CVE) · Technical impact partial (CVSS below 9.0). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

November 15, 2021

Last Modified

November 21, 2024

Advisory Details (2)

Auto-updated Sep 5, 2026
Patch available. Sources: github_commit, github.
githubMentions a patch (unverified)

Secure/signed cookies share secrets between sites in a multi-site application · Advisory · discourse/rails_multisite · GitHub

Affected: v4 of the

https://github.com/discourse/rails_multisite/security/advisories/GHSA-844m-cpr9-jcmh
github_commit

commit c6785cdb5c92 (discourse/rails_multisite)

Fix landed in discourse/rails_multisite commit c6785cdb5c92 — awaiting tagged release

https://github.com/discourse/rails_multisite/commit/c6785cdb5c9277dd2c5ac8d55180dd1ece440ed0

Affected Packages

(1 across 1 ecosystem)
RubyGems(1)
PackageVulnerable rangeFix by version rangeDependents
rails_multisite0.0.1 ... 3.1.0 (28 versions)
  • every version up to 4.0.0: fixed in 4.0.0
—

Weakness Classification(3)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 7× in last 7d / 32× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 186 total refreshes for this CVE.

  1. 2026-10-09 20:04 UTCEPSS rescore
  2. 2026-10-08 16:40 UTCEPSS rescore
  3. 2026-10-07 23:45 UTCEPSS rescore
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  10. 2026-09-30 15:41 UTCEG score recompute
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  17. 2026-09-25 12:45 UTCOSV refresh
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  1. 2026-09-17 19:23 UTCEPSS rescore
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  11. 2026-09-06 03:52 UTCOSV refresh
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  21. 2026-08-28 21:37 UTCEPSS rescore
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  25. 2026-08-24 14:13 UTCEPSS rescore
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  30. 2026-08-19 17:01 UTCEPSS rescore
  31. 2026-08-19 14:32 UTCOSV refresh
  32. 2026-08-18 13:45 UTCEPSS rescore
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  37. 2026-08-13 21:57 UTCEPSS rescore
  38. 2026-08-12 13:48 UTCEPSS rescore
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  40. 2026-08-09 13:44 UTCEPSS rescore
  41. 2026-08-08 16:33 UTCEPSS rescore
  42. 2026-08-07 16:24 UTCEPSS rescore
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  44. 2026-08-05 19:14 UTCEPSS rescore
  45. 2026-08-04 10:34 UTCEPSS rescore
  46. 2026-08-04 10:27 UTCOSV refresh
  47. 2026-08-03 10:33 UTCEPSS rescore
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  50. 2026-07-30 16:25 UTCEPSS rescore
  51. 2026-07-30 01:28 UTCEPSS rescore
  52. 2026-07-28 15:33 UTCEPSS rescore
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  55. 2026-07-25 14:15 UTCEPSS rescore
  56. 2026-07-24 14:15 UTCEPSS rescore
  57. 2026-07-23 14:16 UTCEPSS rescore
  58. 2026-07-23 02:04 UTCEG score recompute
  59. 2026-07-22 22:50 UTCEG score recompute
  60. 2026-07-22 14:06 UTCEPSS rescore
  61. 2026-07-21 15:22 UTCEPSS rescore
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  63. 2026-07-20 17:05 UTCEPSS rescore
  64. 2026-07-19 14:29 UTCEPSS rescore
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  68. 2026-07-18 07:29 UTCOSV refresh
  69. 2026-07-16 17:00 UTCEPSS rescore
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  71. 2026-07-15 16:55 UTCEPSS rescore
  72. 2026-07-15 16:55 UTCEPSS rescore
  73. 2026-07-15 01:58 UTCEPSS rescore
  74. 2026-07-13 22:27 UTCEPSS rescore
  75. 2026-07-13 22:27 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2021-41263?
CVE-2021-41263 is a high vulnerability published on November 15, 2021. railsmultisite provides multi-db support for Rails applications. In affected versions this vulnerability impacts any Rails applications using railsmultisite alongside Rails' signed/encrypted cookies. Depending on how the application makes use of these cookies, it may be possible for an attacker to…
When was CVE-2021-41263 disclosed?
CVE-2021-41263 was first published on November 15, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-41263 actively exploited?
CVE-2021-41263 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.6% probability of exploitation in the next 30 days (48th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2021-41263?
CVE-2021-41263 has a CVSS v3 base score of 8.3 (NVD).
How do I remediate CVE-2021-41263?
A fix for CVE-2021-41263 is available: update to the fixed version the vendor names in its advisory.

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