Discourse: Private Chat Threat Message Disclosure via Chat Onebox Channel/Threat ID Mismatch

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-72724
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-10 16:19:49 UTC
Updated2026-08-10 16:19:49 UTC
DescriptionDiscourse is an open-source discussion platform. Prior to 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0, plugins/chat/lib/chat/onebox_handler.rb resolves Chat::Thread by route thread_id independently of the route channel_id before checking whether the user can preview the selected chat channel. An authenticated user can pair a public channel ID with a private thread ID in a /onebox.json request and obtain private thread message content. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0.

Risk And Classification

Primary CVSS: v3.1 4.3 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Problem Types: CWE-639 | CWE-639 CWE-639: Authorization Bypass Through User-Controlled Key

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary4.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
3.1CNADECLARED4.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Discourse Discourse affected < 2026.1.6 Not specified
CNA Discourse Discourse affected >= 2026.5.0-latest, < 2026.5.2 Not specified
CNA Discourse Discourse affected >= 2026.6.0-latest, < 2026.6.1 Not specified
CNA Discourse Discourse affected >= 2026.7.0-latest, < 2026.7.0 Not specified

References

ReferenceSourceLinkTags
github.com/discourse/discourse/commit/1276d7032af8803956c74ae87ccfd97693... [email protected] github.com
github.com/discourse/discourse/commit/dc54846f0754799591717b6018343e4952... [email protected] github.com
github.com/discourse/discourse/commit/45ab6d54076de9ca4965888974d4416d5b... [email protected] github.com
github.com/discourse/discourse/pull/42093 [email protected] github.com
github.com/discourse/discourse/commit/49efe1d7f098f2ce7301908815a211cc92... [email protected] github.com
github.com/discourse/discourse/security/advisories/GHSA-8g98-fvfc-9w48 [email protected] github.com
github.com/discourse/discourse/pull/42092 [email protected] github.com
github.com/discourse/discourse/pull/42091 [email protected] github.com
github.com/discourse/discourse/pull/42094 [email protected] github.com
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