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CVE-2026-91156— Discourse: Chat MessageBus delivers read-restricted messages to unauthorized users

Quick assessment

Affected
discourse discourse
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Discourse 是一个开源的讨论平台。在版本 2026.9.0、2026.8.1、2026.7.3 和 2026.1.9 之前，MessageBus 的受众计算机制存在缺陷，可能导致将来自具有阅读限制类别的聊天频道的消息，发送给那些虽可查看该类别但根据站点组权限限制无权使用聊天功能的已认证用户。由于发布路径仅依据类别可见性对事件进行了边界控制，而未同时强制实施聊天功能的使用资格检查，因此暴露了 MessageBus 积压消息中可访问的实时及最近消息内容。该漏洞不允许通过聊天 API 检索频道完整历史消息，也不允

CVSS 7.5 · High EPSS 0.48% · P40

Possible ATT&CK Techniques 1 AI

T1530 · Data from Cloud Storage

Affected Version Matrix 4

VendorProduct Version RangeStatus
discourse discourse < 2026.1.9 affected
>= 2026.7.0-latest, < 2026.7.3 affected
>= 2026.8.0-latest, < 2026.8.1 affected
>= 2026.9.0-latest, < 2026.9.0 affected
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I. Basic Information for CVE-2026-91156

Vulnerability Information
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Vulnerability Title
Discourse: Chat MessageBus delivers read-restricted messages to unauthorized users
Source: CVE Program / CVE List V5
Vulnerability Description
Discourse is an open-source discussion platform. Prior to 2026.9.0, 2026.8.1, 2026.7.3, and 2026.1.9, MessageBus audience calculation could deliver messages from a read-restricted category chat channel to an authenticated user who could view the category but was not allowed to use Chat under the site's group restrictions. The publication path bounded events by category visibility without also enforcing Chat eligibility, exposing live and recent message content available in the MessageBus backlog. The issue does not permit retrieval of the channel's full history through the Chat API and does not permit message creation or modification. This issue is fixed in versions 2026.9.0, 2026.8.1, 2026.7.3, and 2026.1.9.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制缺失
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
discourse discourse < 2026.1.9 -

II. Public POCs for CVE-2026-91156

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III. Intelligence Information for CVE-2026-91156

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Patches & Fixes for CVE-2026-91156 (4)

Same Patch Batch · discourse · 2026-10-14 · 3 CVEs total

CVE-2026-91159 7.7 HIGH Discourse: Stored oEmbed HTML injection via allowed iframe
CVE-2026-91157 7.5 HIGH Discourse: Media uploads remain publicly accessible after category permissions are restric

IV. Related Vulnerabilities

Same product: discourse
Same vendor: discourse
Same weakness: CWE-862

V. Comments for CVE-2026-91156

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