dbcve.org
DiscourseApplication

CVE-2026-27934

HIGH · 7.5 CVSS v3.1 Published 2026-03-19
Fix available
A fix is available. Upgrade to 2026.1.2 / 2026.2.1 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Discourse is an open-source discussion platform. Versions prior to 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 have a lack of visibility checks with a user action API endpoint that results in disclosure of the title and post excerpt to unauthorized users, leading to information disclosure. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. No known workarounds are available.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Discourse versions prior to 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a user action API endpoint that lacks proper visibility/authorization checks, allowing unauthenticated or unauthorized users to retrieve post titles and excerpts they should not have access to, resulting in sensitive information disclosure.

MitigationUpgrade Discourse to version 2026.3.0-latest.1, 2026.2.1, or 2026.1.2 or later to apply the patch that adds proper visibility checks to the affected API endpoint.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
DiscourseApplication
Affected:>= 2026.1.0, < 2026.1.2>= 2026.2.0, < 2026.2.1= 2026.3.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Discourse version
    Run `cat /var/discourse/version` or check the Discourse admin dashboard under /about for the currently installed version number
    Affected if The installed version is >= 2026.1.0 and < 2026.1.2, OR >= 2026.2.0 and < 2026.2.1, OR equals 2026.3.0
  2. Check API endpoint accessibility
    Attempt a curl request to the user action API endpoint (typically /user_actions.json or similar) without authentication or with a low-privilege account to see if post titles or excerpts are returned
    Affected if Post titles or excerpts are returned for posts the requesting user should not have visibility to based on category permissions or topic visibility settings
  3. Verify authentication requirement on user actions API
    Inspect the Rails route definition for user action endpoints in config/routes.rb or test the endpoint behavior with an invalid or missing API key
    Affected if The endpoint responds without requiring valid authentication or returns data regardless of session status
  4. Review user role permissions
    Check the Discourse admin panel under /admin/site_settings/category/login for related authentication settings, and verify that the user_actions endpoint enforces the same visibility rules as the web interface
    Affected if API responses bypass category or topic visibility restrictions that apply to regular web access

You are affected if your Discourse installation runs a version between 2026.1.0 and 2026.3.0 (exclusive of the fixed releases) and the user actions API endpoint returns post titles or excerpts without proper visibility enforcement.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2026.1.2 / 2026.2.1 or later
Fixed in 2026.1.22026.2.1
Interim mitigation

Upgrade Discourse to version 2026.3.0-latest.1, 2026.2.1, or 2026.1.2 or later to apply the patch that adds proper visibility checks to the affected API endpoint.

Recommended fix High confidence

2026.3.0-latest.1 (or 2026.2.1 / 2026.1.2 depending on your current branch)

  1. Identify your current Discourse version by checking the /admin dashboard or running `discourse version`
  2. Determine which stable branch you are on (2026.1, 2026.2, or 2026.3)
  3. Upgrade Discourse to the patched version for your branch: 2026.1.2 for the 2026.1 branch, 2026.2.1 for the 2026.2 branch, or 2026.3.0-latest.1 for the 2026.3 branch
  4. Verify the upgrade completed successfully and the version matches the expected patched release
  5. Test that the user action API endpoint now properly enforces visibility checks

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Discourse Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,408.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-27934 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-27934 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data