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DiscourseApplication

CVE-2026-33425

MEDIUM · 5.3 CVSS v3.1 Published 2026-03-21
Fix available
A fix is available. Upgrade to 2026.1.2 / 2026.2.1 or later.
See remediation →
62/100
Remediation priority · Elevated
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. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, unauthenticated users can determine whether a specific user is a member of a private group by observing changes in directory results when using the `exclude_groups` parameter. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. As a workaround, disable public access to the user directory via Admin → Settings → hide user profiles from public.

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

In Discourse prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, an unauthenticated attacker can determine if a specific user is a member of a private group by manipulating the exclude_groups parameter in the user directory endpoint and observing differences in the returned results. This allows enumeration of private group membership.

MitigationUpdate to Discourse versions 2026.3.0-latest.1, 2026.2.1, or 2026.1.2, or as a workaround temporarily disable public access to the user directory via Admin → Settings → hide user profiles from public.

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
Low
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/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. Check Discourse version
    Log into the Discourse admin panel and navigate to /about or check the version indicator in the footer. Alternatively, access the /about endpoint via API to retrieve the 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 (any version in the affected ranges listed).
  2. Verify user directory access settings
    In Discourse admin panel, go to Settings and search for 'hide user profiles from public'. Check whether this setting is enabled or disabled.
    Affected if The setting 'hide user profiles from public' is disabled, meaning the user directory is publicly accessible to unauthenticated users.
  3. Test the exclude_groups parameter behavior
    As an unauthenticated user, access the user directory endpoint (typically /directory.json) with different exclude_groups parameter values and observe whether responses differ based on private group membership. Compare results with and without specific exclude_groups values to see if private group information leaks.
    Affected if The endpoint returns different user listings when exclude_groups is manipulated, allowing inference of private group membership through response differences.

You are affected if your Discourse version falls within the affected ranges AND the user directory is publicly accessible, allowing unauthenticated enumeration of private group membership via the exclude_groups parameter.

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

Update to Discourse versions 2026.3.0-latest.1, 2026.2.1, or 2026.1.2, or as a workaround temporarily disable public access to the user directory via Admin → Settings → hide user profiles from public.

Recommended fix High confidence

2026.1.2 (for 2026.1.x) | 2026.2.1 (for 2026.2.x) | 2026.3.0-latest.1 (for 2026.3.0)

  1. Backup your Discourse instance database and files before upgrading
  2. Identify your current Discourse version from the /admin dashboard or by running `git log -1` in your container
  3. If running 2026.1.x branch, upgrade to version 2026.1.2
  4. If running 2026.2.x branch, upgrade to version 2026.2.1
  5. If running 2026.3.0, upgrade to version 2026.3.0-latest.1
  6. Run the Discourse upgrade command appropriate to your installation method (e.g., `./launcher rebuild app` for Docker installations)
  7. After upgrade, verify the version by visiting /admin dashboard
  8. Confirm the vulnerability is resolved by testing that the exclude_groups parameter no longer reveals private group membership information
Caveat Standard Discourse upgrade considerations apply - test in staging first, ensure plugins are compatible

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

Fix this in Discourse Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing1.0 h
  • Review / QA1.0 h
5.0 hours of engineering $890
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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-2026-33425 in production — separate from our analysis above.

No notes yet

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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