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

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.

Published: 2026-01-28 Last update: 2026-01-30 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-21865 is rated Low Risk (31.5/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.05%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-21865

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-13 0.03% 0.05% +0.02%
2 2026-01-29 — 0.03% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-21865

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:H)
They need powerful rights—admin, root, or similar—before this pays off.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 1.2 5.2 [email protected]

Weakness enumeration for CVE-2026-21865

Affected software / configurations for CVE-2026-21865

Vendor Product Version Raw CPE
discourse discourse < 3.5.4 cpe:2.3:a:discourse:discourse:*:*:*:*:stable:*:*:*
discourse discourse >= 2025.11.0, < 2025.11.2 cpe:2.3:a:discourse:discourse:*:*:*:*:stable:*:*:*
discourse discourse 2025.12.0 cpe:2.3:a:discourse:discourse:2025.12.0:*:*:*:stable:*:*:*
discourse discourse 2026.1.0 cpe:2.3:a:discourse:discourse:2026.1.0:*:*:*:stable:*:*:*

References for CVE-2026-21865

cvelogic Threat Intelligence