Auth bypass in Discourse

CVE-2026-27151

Discourse is an open source discussion platform. Prior to versions 2025.12.2, 2026.1.1, and 2026.2.0, the `move_posts` action only checked `can_move_posts?` on the source topic but never validated write permissions on the destination topic. This allowed TL4 users and category group moderators to move posts into topics in categories where they lack posting privileges (e.g., read-only categories or categories with group-restricted write access). Versions 2025.12.2, 2026.1.1, and 2026.2.0 patch the issue. No known workarounds are available.

Vulnerability class: Broken Access Control

Published · last modified .

CVSS v3 metric

CVSS v3 base score 2.7 (Low). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:N.

EPSS exploit prediction

EPSS: 0.003 (17.1th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 17th percentile — 17.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-27151: held from 0.002 to 0.003.

EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001

Affected products

  • Discourse — versions >= 2026.2.0-latest, < 2026.2.0, >= 2026.1.0-latest, < 2026.1.1, 2026.2.0

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-27151?
CVE-2026-27151 is a low-severity vulnerability in Discourse, classified under Missing Authorization. CVSS score: 2.7/10. Published 2026-02-26.
How severe is CVE-2026-27151?
Low severity. CVSS v3 base score is 2.7 out of 10.