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DiscourseApplication

CVE-2026-45775

MEDIUM · 6.8 CVSS v3.1 Published 2026-06-12
Fix available
A fix is available. Upgrade to 2026.1.0 / 2026.1.4 or later.
See remediation →
74/100
Remediation priority · Elevated
Remotely reachable 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. From versions 2026.1.0-latest to before 2026.1.4, 2026.3.0-latest to before 2026.3.1, and 2026.4.0-latest to before 2026.4.1, a path traversal vulnerability in Discourse backup handling could allow an authenticated administrator on one site in a multisite deployment to access backup files belonging to another site when backups are stored locally. In affected configurations, an admin on Site A could potentially retrieve sensitive backup data from Site B (same host, multisite) by crafting a backup download request with a traversal payload. This issue has been patched in versions 2026.1.4, 2026.3.1, 2026.4.1, and 2026.5.0-latest.1.

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

A path traversal vulnerability in Discourse's backup handling allows an authenticated administrator on one site in a multisite deployment to access backup files belonging to another site on the same host by crafting a backup download request with directory traversal sequences (e.g., ../). This affects configurations where backups are stored locally.

MitigationUpgrade Discourse to version 2026.1.4, 2026.3.1, 2026.4.1, or 2026.5.0-latest.1 or later. In the meantime, restrict administrative access and monitor for suspicious backup download requests with traversal patterns.

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>= 2026.1.0, < 2026.1.4>= 2026.3.0, < 2026.3.1>= 2026.4.0, < 2026.4.1= 2026.5.0

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
High
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/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
    Run `cd /var/discourse && git pull && git rev-parse HEAD` or check the version file at /var/discourse/version, or access the admin dashboard and look at the version number displayed
    Affected if The installed version is < 2026.1.4, 2026.3.0 to < 2026.3.1, 2026.4.0 to < 2026.4.1, or exactly 2026.5.0
  2. Confirm multisite configuration
    Check if multisite is enabled by reviewing the container config at /var/discourse/discourse.yml or running `RAILS_ENV=production rake multisite:machines` from the discourse directory
    Affected if Multisite is enabled and multiple sites share the same host
  3. Verify local backup storage
    Check the backup settings in the Discourse admin panel under /admin/backups or review the discourse.yml configuration for `backup_location: local`
    Affected if Backups are configured to be stored locally rather than on external storage like S3
  4. Inspect backup download requests
    Review web server logs (nginx access logs) and Discourse logs for backup download requests containing directory traversal patterns such as `../` in the URL parameters
    Affected if There are logged backup download requests with traversal sequences targeting files from other sites

A user is affected if their Discourse version falls within the affected ranges, multisite is enabled, backups are stored locally, and no mitigations have been applied to restrict backup file access between sites.

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 2026.1.0 / 2026.1.4 / 2026.3.1 or later
Fixed in 2026.1.02026.1.42026.3.1
Interim mitigation

Upgrade Discourse to version 2026.1.4, 2026.3.1, 2026.4.1, or 2026.5.0-latest.1 or later. In the meantime, restrict administrative access and monitor for suspicious backup download requests with traversal patterns.

Recommended fix High confidence

2026.5.0-latest.1 (or 2026.1.4/2026.3.1/2026.4.1 depending on your release branch)

  1. 1. Identify your current Discourse version by checking the admin dashboard or running `git log -1` in your Discourse installation directory
  2. 2. Plan for upgrade maintenance window - schedule during low-traffic period
  3. 3. Take a full backup of your Discourse instance before upgrading
  4. 4. Upgrade Discourse to version 2026.5.0-latest.1 (or minimum 2026.1.4, 2026.3.1, or 2026.4.1 depending on your branch)
  5. 5. Verify the upgrade completed successfully by checking the admin dashboard version display
  6. 6. Test backup functionality in a multisite environment to confirm the vulnerability is resolved

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

Fix this in Discourse Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
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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-2026-45775 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