CVE-2026-91122
Discourse: Chat MessageBus delivers read-restricted messages to unauthorized users
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
Description
Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the video placeholder component allowed crafted HTML to cause an attribute breakout and inject an attacker-controlled event handler. An authenticated user with default trust-level posting privileges could store the crafted placeholder in a post. When another user opened the post and clicked the video play overlay, the handler could execute arbitrary JavaScript in the viewer's session. Default Content Security Policy settings block inline event handlers, but instances with CSP disabled or relaxed could allow the script to read page content and make authenticated requests as the viewer. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | High8.7 | CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N |
| NVDNVD · Deferred | 3.1 | High8.7 | CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N |
- EPSS (exploitation in 30 days)
- 0.26% · top 82% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.7.
Weakness
Affected products
References (6)
- https://github.com/discourse/discourse/security/advisories/GHSA-8m44-f6g9-7cg7 (opens in a new tab)x_refsource_CONFIRM
- https://github.com/discourse/discourse/pull/42882 (opens in a new tab)x_refsource_MISC
- https://github.com/discourse/discourse/commit/05d92b8749f68d2626cbe65ec7adde7562a0283d (opens in a new tab)x_refsource_MISC
- https://github.com/discourse/discourse/commit/5674b3e6594825c28d2678e55057fd6802f11031 (opens in a new tab)x_refsource_MISC
- https://github.com/discourse/discourse/commit/c3993e318e172389be5c98455177876f1dd87dda (opens in a new tab)x_refsource_MISC
- https://github.com/discourse/discourse/commit/d7126af3264b672d2201d84c18a37cb8627424a8 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-91122)Record last updated .