Auth bypass in Discourse
CVE-2026-27491
Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, a type coercion issue in a post actions API endpoint allowed non-staff users to issue warnings to other users. Warnings are a staff-only moderation feature. The vulnerability required the attacker to be a logged-in user and to send a specifically crafted request. No data exposure or privilege escalation beyond the ability to create unauthorized user warnings was possible. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. No known workarounds are available.
Vulnerability class: Broken Access Control
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N.
EPSS exploit prediction
EPSS: 0.003 (25.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 25th percentile — 25.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: +0.000
Affected products
- Discourse — versions = 2026.3.0-latest, >= 2026.2.0-latest, < 2026.2.1, >= 2026.1.0-latest, < 2026.1.2
Weakness classification (CWE)
References
- github.com/discourse/discourse/security/advisories/GHSA-xq37-5fvf-4m4j (Vendor Advisory)
- github.com/discourse/discourse/commit/60a588f4da4ab0feceb2c44787d4261b4f8757be (Patch)
- github.com/discourse/discourse/commit/d3cb203feabc46d765ecb91f348613a2bd531b89 (Patch)
- github.com/discourse/discourse/commit/f5fef73827da7520efc517357bd2a6bab35d7886 (Patch)
Frequently asked questions
- What is CVE-2026-27491?
- CVE-2026-27491 is a medium-severity vulnerability in Discourse, classified under Missing Authorization. CVSS score: 4.3/10. Published 2026-03-19.
- How severe is CVE-2026-27491?
- Medium severity. CVSS v3 base score is 4.3 out of 10.