Discourse: Chat MessageBus delivers read-restricted messages to unauthorized users

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-91122
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-24 17:17:08 UTC
Updated2026-09-24 18:19:06 UTC
DescriptionDiscourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the video placeholder component allowed crafted HTML to cause an attribute breakout and inject an attacker-controlled event handler. An authenticated user with default trust-level posting privileges could store the crafted placeholder in a post. When another user opened the post and clicked the video play overlay, the handler could execute arbitrary JavaScript in the viewer's session. Default Content Security Policy settings block inline event handlers, but instances with CSP disabled or relaxed could allow the script to read page content and make authenticated requests as the viewer. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.

Risk And Classification

Primary CVSS: v3.1 8.7 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

Problem Types: CWE-79 | CWE-79 CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary8.7HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N
3.1CNADECLARED8.7HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
Required
Scope
Changed
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Discourse Discourse affected < 2026.8.0 Not specified
CNA Discourse Discourse affected >= 2026.7.0-latest, < 2026.7.2 Not specified
CNA Discourse Discourse affected >= 2026.6.0-latest, < 2026.6.3 Not specified
CNA Discourse Discourse affected >= 2026.1.0-latest, < 2026.1.8 Not specified

References

ReferenceSourceLinkTags
github.com/discourse/discourse/commit/c3993e318e172389be5c98455177876f1d... [email protected] github.com
github.com/discourse/discourse/commit/05d92b8749f68d2626cbe65ec7adde7562... [email protected] github.com
github.com/discourse/discourse/commit/5674b3e6594825c28d2678e55057fd6802... [email protected] github.com
github.com/discourse/discourse/pull/42882 [email protected] github.com
github.com/discourse/discourse/security/advisories/GHSA-8m44-f6g9-7cg7 [email protected] github.com
github.com/discourse/discourse/commit/d7126af3264b672d2201d84c18a37cb862... [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

© CVE.report 2026

Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties, implied or otherwise, with regard to this information or its use. Any use of this information is at the user's risk. It is the responsibility of user to evaluate the accuracy, completeness or usefulness of any information, opinion, advice or other content. EACH USER WILL BE SOLELY RESPONSIBLE FOR ANY consequences of his or her direct or indirect use of this web site. ALL WARRANTIES OF ANY KIND ARE EXPRESSLY DISCLAIMED. This site will NOT BE LIABLE FOR ANY DIRECT, INDIRECT or any other kind of loss.

CVE, CWE, and OVAL are registred trademarks of The MITRE Corporation and the authoritative source of CVE content is MITRE's CVE web site. This site includes MITRE data granted under the following license.

Free CVE JSON API cve.report/api

CVE.report and Source URL Uptime Status status.cve.report