Discourse prior 3.5.4/2025.11.2/2025.12.1/2026.1.0 Personal Message authorization

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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5.5$0-$5k0.00

Summaryinfo

A vulnerability classified as problematic has been found in Discourse. Affected by this vulnerability is an unknown functionality of the component Personal Message Handler. This manipulation causes authorization. This vulnerability is handled as CVE-2026-21865. The attack can be initiated remotely. There is not any exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Discourse. It has been declared as problematic. Affected by this vulnerability is some unknown processing of the component Personal Message Handler. The manipulation with an unknown input leads to a authorization vulnerability. The CWE definition for the vulnerability is CWE-862. The product does not perform an authorization check when an actor attempts to access a resource or perform an action. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-21865 since 01/05/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation needs additional levels of successful authentication. Neither technical details nor an exploit are publicly available.

Upgrading to version 3.5.4, 2025.11.2, 2025.12.1 or 2026.1.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-4874). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

Name

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.6
VulDB Meta Temp Score: 5.5

VulDB Base Score: 4.7
VulDB Temp Score: 4.5
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 6.5
CNA Vector (GitHub_M): 🔒

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Authorization
CWE: CWE-862 / CWE-863 / CWE-285
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Discourse 3.5.4/2025.11.2/2025.12.1/2026.1.0

Timelineinfo

01/05/2026 CVE reserved
01/29/2026 +24 days Advisory disclosed
01/29/2026 +0 days VulDB entry created
01/29/2026 +0 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: GHSA-4777-wrv5-3g39
Status: Confirmed

CVE: CVE-2026-21865 (🔒)
GCVE (CVE): GCVE-0-2026-21865
GCVE (VulDB): GCVE-100-343321
EUVD: 🔒

Entryinfo

Created: 01/29/2026 06:27
Updated: 01/29/2026 23:27
Changes: 01/29/2026 06:27 (63), 01/29/2026 23:27 (1)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Discussion

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