CVE-2026-21865

Summary

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.

Affected Software

VendorProductVersion RangeStatus
discoursediscourse< 3.5.4affected
discoursediscourse>= 2025.11.0-latest, < 2025.11.2affected
discoursediscourse>= 2025.12.0-latest, < 2025.12.1affected
discoursediscourse>= 2026.1.0-latest, < 2026.1.0affected

Weaknesses

  • CWE-862: CWE-862: Missing Authorization

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

References