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DiscourseApplication

CVE-2026-27936

MEDIUM · 5.3 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 →
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, a restriction bypass allows restricted post action counts to be disclosed to non-privileged users through a carefully crafted request. 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 · moderate confidence

Discourse versions prior to 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain an authorization bypass allowing non-privileged users to discover restricted post action counts (e.g., likes, flags, bookmarks) through a crafted API request. The vulnerability stems from improper enforcement of access controls on post action metadata.

MitigationUpgrade Discourse to version 2026.3.0-latest.1, 2026.2.1, or 2026.1.2. No workarounds are available.

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. Identify installed Discourse version
    Access the Discourse admin panel at /admin, or run 'git log' in the Discourse installation directory, or check the VERSION file in the Discourse root if available
    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 exactly
  2. Verify API endpoint accessibility
    Send a crafted GET request to the /posts/{id}/actions.json endpoint for a restricted or private post while authenticated as a non-privileged (non-staff) user
    Affected if The API response returns action counts (likes, flags, bookmarks) that should be hidden from non-privileged users, indicating the authorization bypass is present
  3. Check user role permissions
    In the Discourse admin panel under /admin/users, verify whether standard/trust_level users exist and whether certain categories or posts have restricted visibility settings
    Affected if Non-privileged users have access to view restricted content through the API but should not be able to see the action counts according to access controls

A user is affected if their Discourse installation version falls within 2026.1.0 to 2026.1.11, 2026.2.0 to 2026.2.0, or equals 2026.3.0, AND the API endpoint returns restricted post action counts to non-privileged users.

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. No workarounds are available.

Recommended fix High confidence

2026.3.0-latest.1 (or 2026.2.1 / 2026.1.2 depending on your release track)

  1. Identify your current Discourse version by checking the admin dashboard or running discourse version command
  2. Stop the Discourse application to prevent data inconsistency during upgrade
  3. Backup your Discourse database and uploaded files following standard backup procedures
  4. Upgrade to a fixed release: 2026.1.2, 2026.2.1, or 2026.3.0-latest.1 (prefer the latest for most recent security patches)
  5. Follow the official Discourse upgrade guide for your deployment method (e.g., ./launcher rebuild app for Docker installations)
  6. Verify the upgrade was successful by checking the version in the admin dashboard
  7. Test that restricted post action counts are now properly protected from non-privileged users
Caveat Standard Discourse upgrade risks apply - review release notes for your target version for any breaking changes or required migration steps

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

Fix this in Discourse Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,780
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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-2026-27936 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