Discourse: Private Chat Threat Message Disclosure via Chat Onebox Channel/Threat ID Mismatch
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 4.3epss 0.5%
exploitation probability
0.5%top 61% of all CVEs
observed exploitation
nono source reports it
Discourse 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.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Affected products
discourse · discourseReferences
https://github.com/discourse/discourse/commit/1276d7032af8803956c74ae87ccfd976938dcd75https://github.com/discourse/discourse/commit/45ab6d54076de9ca4965888974d4416d5b48e83chttps://github.com/discourse/discourse/commit/49efe1d7f098f2ce7301908815a211cc9248270fhttps://github.com/discourse/discourse/commit/dc54846f0754799591717b6018343e49524e41cehttps://github.com/discourse/discourse/pull/42091https://github.com/discourse/discourse/pull/42092https://github.com/discourse/discourse/pull/42093https://github.com/discourse/discourse/pull/42094https://github.com/discourse/discourse/security/advisories/GHSA-8g98-fvfc-9w48