CVE-2021-41263Network attack vector

Cross-site cookie reuse via host-agnostic salts

Published Nov 15, 2021 · Updated Aug 4, 2024

Cookie isolation failure in Discourse Rails Multisite before 4.0.0 allows remote authenticated users to reuse cookies across tenant sites. Before 4.0.0, middleware leaves Rails action_dispatch cookie salts unchanged across host switches, so tenants sharing secret_key_base derive interchangeable cookie keys. The attack requires signed or encrypted cookies and a valid cookie from another tenant; access is limited to the authority or data represented by that cookie.

CVSS severity6.2
Medium
EPSS probability0.63%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cookie isolation failure in Discourse Rails Multisite before 4.0.0 allows remote authenticated users to reuse cookies across tenant sites. Before 4.0.0, middleware leaves Rails action_dispatch cookie salts unchanged across host switches, so tenants sharing secret_key_base derive interchangeable cookie keys. The attack requires signed or encrypted cookies and a valid cookie from another tenant; access is limited to the authority or data represented by that cookie.

The record

CVE
CVE-2021-41263
Published
Nov 15, 2021
Updated
Aug 4, 2024
Vendor
Discourse
Product
Rails Multisite
Classifications
CWE-200, CWE-565, CWE-327, T1550.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 4.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Discourse · Rails Multisiteversion=< 4.0.0

Published CVSS scores

6.2GitHub Security AdvisoryCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:L/A:H
6.0NIST NVDAV:N/AC:M/Au:S/C:P/I:P/A:P
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-200Exposure of Sensitive Information to an Unauthorized Actor
CWE-565Reliance on Cookies without Validation and Integrity Checking
CWE-327Use of a Broken or Risky Cryptographic Algorithm
T1550.004Use Alternate Authentication Material: Web Session Cookie

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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