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DiscourseApplication

CVE-2026-49256

HIGH · 7.5 CVSS v3.1 Published 2026-07-09
Fix available
A fix is available. Upgrade to 2026.1.5 / 2026.4.2 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click 6 weeks old

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 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5, restricted tag and tag-group names attached to publicly readable categories as allowed_tags, allowed_tag_groups, or required tag groups could leak to anonymous and unauthorized users through category and group endpoints. This issue is fixed in versions 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5.

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 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.15 expose restricted tag and tag-group names to anonymous users through category and group endpoints when those tags are attached to publicly readable categories via allowed_tags, allowed_tag_groups, or required_tag_groups attributes, enabling unauthorized information disclosure.

MitigationUpgrade Discourse to version 2026.6.0, 2026.5.1, 2026.4.2, or 2026.1.15 or later to patch the information disclosure vulnerability.

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, < 2026.1.5>= 2026.4.0, < 2026.4.2>= 2026.5.0, < 2026.5.1= 2026.6.0

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. Check Discourse version
    Log into the Discourse admin panel and navigate to /admin/about or run `discourse --version` from the command line if you have shell access
    Affected if The installed version matches any of the affected ranges: >= 2026.1.0 and < 2026.1.5, >= 2026.4.0 and < 2026.4.2, >= 2026.5.0 and < 2026.5.1, or exactly 2026.6.0
  2. Identify public categories with tag restrictions
    In the admin panel, navigate to Categories and examine each category set to 'Public' or 'Logged In Users' access. For each public category, check the Tags section for entries in 'Allowed tags', 'Allowed tag groups', or 'Required tag groups' fields
    Affected if Any public category has restricted tags assigned via allowed_tags, allowed_tag_groups, or required_tag_groups that should otherwise be hidden from anonymous users
  3. Verify tag visibility through API endpoints
    Make an unauthenticated (anonymous) HTTP request to the category endpoint (e.g., GET /c/category-slug.json) and group endpoint (e.g., /groups.json) for categories that have restricted tags attached
    Affected if The API response for public categories includes tag names that are marked as staff-only, restricted, or should not be visible to anonymous users

You are affected if your Discourse version is within the vulnerable ranges AND you have public categories with restricted tags assigned through allowed_tags, allowed_tag_groups, or required_tag_groups attributes visible to anonymous 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 2026.1.5 / 2026.4.2 / 2026.5.1 or later
Fixed in 2026.1.52026.4.22026.5.1
Interim mitigation

Upgrade Discourse to version 2026.6.0, 2026.5.1, 2026.4.2, or 2026.1.15 or later to patch the information disclosure vulnerability.

Recommended fix High confidence

2026.6.0 (or latest stable release)

  1. 1. Backup your Discourse instance database and any custom configurations.
  2. 2. Ensure you have SSH access to the server hosting your Discourse installation.
  3. 3. Navigate to your Discourse installation directory (typically /var/www/discourse).
  4. 4. Run the Discourse upgrade command: `sudo ./launcher rebuild app` or `cd /var/www/discourse && git pull && ./bin/rake db:migrate`.
  5. 5. Alternatively, if using the official Docker setup, run: `sudo ./launcher stop app`, then `sudo ./launcher start app` after pulling latest changes.
  6. 6. Verify the upgrade completed successfully by checking the Discourse admin panel for the new version number.
  7. 7. Test that category and tag endpoints no longer expose restricted tag information to anonymous users.

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

Fix this in Discourse Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing4.0 h
  • Review / QA2.0 h
9.0 hours of engineering $1,540
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Scan for this in your stack

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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-2026-49256 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