Auth bypass in Discourse

CVE-2026-26207

Discourse is an open source discussion platform. Prior to versions 2025.12.2, 2026.1.1, and 2026.2.0, `discourse-policy` plugin allows any authenticated user to interact with policies on posts they do not have permission to view. The `PolicyController` loads posts by ID without verifying the current user's access, enabling policy group members to accept/unaccept policies on posts in private categories or PMs they cannot see and any authenticated user to enumerate which post IDs have policies attached via differentiated error responses (information disclosure). The issue is patched in versions 2025.12.2, 2026.1.1, and 2026.2.0 by adding a `guardian.can_see?(@post)` check in the `set_post` before_action, ensuring post visibility is verified before any policy action is processed. As a workaround, disabling the discourse-policy plugin (`policy_enabled = false`) eliminates the vulnerability. There is no other workaround without upgrading.

Vulnerability class: Broken Access Control

Published · last modified .

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.003 (15.6th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 16th percentile — 15.6% 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-2026-26207: 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-2026-26207?
CVE-2026-26207 is a medium-severity vulnerability in Discourse, classified under Missing Authorization. CVSS score: 5.4/10. Published 2026-02-26.
How severe is CVE-2026-26207?
Medium severity. CVSS v3 base score is 5.4 out of 10.