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CVE-2026-21865— Discourse topic conversion permission vulnerability for moderators

CVSS 6.5 · Medium EPSS 0.04% · P12
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I. Basic Information for CVE-2026-21865

Vulnerability Information
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Vulnerability Title
Discourse topic conversion permission vulnerability for moderators
Source: NVD (National Vulnerability Database)
Vulnerability Description
Discourse is an open source discussion platform. In versions prior to 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0, moderators can convert some personal messages to public topics when they shouldn't have access. This issue is patched in versions 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0. As a workaround, site admin can temporarily revoke the moderation role from untrusted moderators or remove the moderator group from the "personal message enabled groups" site setting until the Discourse instance has been upgraded to a version that has been patched.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N
Source: NVD (National Vulnerability Database)
Vulnerability Type
授权机制缺失
Source: NVD (National Vulnerability Database)
Vulnerability Title
Discourse 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Discourse是Discourse开源的一套开源的社区讨论平台。该平台包括社区、电子邮件和聊天室等功能。 Discourse 3.5.4之前版本、2025.11.2之前版本、2025.12.1之前版本和2026.1.0之前版本存在安全漏洞，该漏洞源于访问控制不当，可能导致版主将私人消息转换为公开主题。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

VendorProductAffected VersionsCPESubscribe
discoursediscourse < 3.5.4 -

II. Public POCs for CVE-2026-21865

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III. Intelligence Information for CVE-2026-21865

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Same Patch Batch · discourse · 2026-01-28 · 14 CVEs total

CVE-2025-686627.6 HIGHFinalDestination hostname matching allows SSRF protection bypass
CVE-2025-684797.1 HIGHDiscourse subscriptions are susceptible to takeover
CVE-2025-689336.9 MEDIUMDiscourse non-admin moderators can exfiltrate private content via post ownership transfer
CVE-2026-247426.5 MEDIUMDiscourse staff action logs expose sensitive information to moderators
CVE-2025-689346.5 MEDIUMDiscourse Has Denial of Service (DoS) Vulnerability in Drafts Creation Endpoint
CVE-2025-677234.6 MEDIUMDiscourse vulnerable to stored Cross-site Scripting via Katex in discourse-math plugin
CVE-2025-664884.6 MEDIUMDiscourse allows script execution in uploaded HTML/XML files on S3
CVE-2025-686594.3 MEDIUMDiscourse has DoS vulnerability in username change endpoint
CVE-2026-23743Discourse allows permalinks to restricted resources to leak resource slugs to unauthorized
CVE-2025-69289Discourse has insecure default configuration that allows non-admin moderators to takeover
CVE-2025-69218Discourse moderators can access admin-only reports exposing private upload URLs
CVE-2025-68666Discourse users archives leaked to users with moderation privileges
CVE-2025-68660Discourse AI Discover's continue conversation allows threat actor to impersonate user

IV. Related Vulnerabilities

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

V. Comments for CVE-2026-21865

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