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DiscourseApplication

CVE-2023-41043

MEDIUM · 6.5 CVSS v3.1 Published 2023-09-15
Fix available
A fix is available. Upgrade to 3.1.1 or later.
See remediation →
71/100
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. Prior to version 3.1.1 of the `stable` branch and version 3.2.0.beta1 of the `beta` and `tests-passed` branches, a malicious admin could create extremely large icons sprites, which would then be cached in each server process. This may cause server processes to be killed and lead to downtime. The issue is patched in version 3.1.1 of the `stable` branch and version 3.2.0.beta1 of the `beta` and `tests-passed` branches. This is only a concern for multisite installations. No action is required when the admins are trusted.

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 versions prior to 3.1.1 (stable) and 3.2.0.beta1 (beta/tests-passed), a malicious administrator on multisite installations can create excessively large icon sprite files. These oversized sprites get cached in each server process memory, potentially causing memory exhaustion that leads to process termination and service downtime.

MitigationUpgrade Discourse to version 3.1.1 or higher (stable) / 3.2.0.beta1 or higher (beta). For multisite deployments where admin trust is a concern, prioritize this update. Environments with only trusted admins on single-site installations are not affected.

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:< 3.1.1= 1.1.0= 1.2.0= 1.3.0= 1.4.0= 1.5.0= 1.6.0= 1.7.0= 1.8.0= 1.9.0= 2.0.0= 2.1.0

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

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. Determine installed Discourse version
    Run `git -C /var/www/discourse describe --tags` or check the version file in the Discourse installation directory. Alternatively, access the /admin dashboard and view the version information at the bottom of the page.
    Affected if The installed version is lower than 3.1.1 (stable) or lower than 3.2.0.beta1 (beta/tests-passed), or matches any version from 1.1.0 through 2.1.0.
  2. Verify if multisite configuration is enabled
    Check for the presence of multiple databases in config/database.yml or look for the `multisite` setting in Discourse configuration files. On the server, run `ls -la /shared/uploads/default/images` and see if there are multiple site directories present.
    Affected if Multisite is enabled (multiple sites share the same Discourse installation).
  3. Locate icon sprite cache files
    Search for sprite files in the Discourse upload directories, typically under /shared/uploads/default/images or within the tmp/cache directory. Use `find /var/www/discourse -name '*sprite*' -type f` to locate sprite-related files.
    Affected if Large sprite files exist that appear unusually large (several megabytes or more) in the cache directories.
  4. Check process memory usage
    Monitor the Rails/Puma worker processes using tools like `htop`, `top`, or by checking memory consumption of Ruby processes. Look for processes with unusually high memory usage that may correspond to cached sprite data.
    Affected if One or more Discourse worker processes consume excessive memory, potentially approaching the point of process termination.

You are affected if your Discourse installation version is below 3.1.1 (or below 3.2.0.beta1 on beta), AND you are running a multisite configuration where an administrator could upload oversized icon sprites.

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 3.1.1 or later
Fixed in 3.1.1
Interim mitigation

Upgrade Discourse to version 3.1.1 or higher (stable) / 3.2.0.beta1 or higher (beta). For multisite deployments where admin trust is a concern, prioritize this update. Environments with only trusted admins on single-site installations are not affected.

Recommended fix High confidence

3.1.1 (stable branch) or 3.2.0.beta1 (beta/tests-passed branches)

  1. Back up your Discourse installation and database before upgrading
  2. Review the official Discourse upgrade guide at https://meta.discourse.org/t/how-to-perform-a-discourse-update/157505
  3. Upgrade to version 3.1.1 or later on the stable branch, or version 3.2.0.beta1 or later on the beta/tests-passed branches
  4. After upgrade, verify the icon sprite system is working correctly by checking that custom icons load properly in the admin interface
  5. For multisite installations, monitor server memory usage to confirm the fix is effective

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

Fix this in Discourse Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,390
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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-2023-41043 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