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MoodleCMS

CVE-2026-26047

MEDIUM · 6.5 CVSS v3.1 Published 2026-02-21
Fix available
A fix is available. Upgrade to 4.5.9 / 5.0.5 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
A denial-of-service vulnerability was identified in Moodle’s TeX formula editor. When rendering TeX content using mimetex, insufficient execution time limits could allow specially crafted formulas to consume excessive server resources. An authenticated user could abuse this behavior to degrade performance or cause service interruption.

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

A denial-of-service vulnerability exists in Moodle's TeX formula editor where the mimetex rendering component lacks sufficient execution time limits. Authenticated users can submit specially crafted TeX formulas that consume excessive server resources, potentially degrading performance or causing service interruption.

MitigationImplement proper execution timeouts and resource limits for mimetex TeX rendering, or update to a patched version of Moodle that addresses the insufficient time limits.

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
MoodleCMS
Affected:< 4.5.9>= 5.0.0, < 5.0.5>= 5.1.0, < 5.1.2

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. Identify Moodle installation version
    Access the site administration area, navigate to Server > Environment or check the version.php file in the Moodle root directory. Alternatively, access /admin/environment.php or view the version constant in lib/moodlelib.php
    Affected if The installed version falls within < 4.5.9 OR >= 5.0.0 AND < 5.0.5 OR >= 5.1.0 AND < 5.1.2
  2. Verify TeX filter is enabled
    Navigate to Site administration > Plugins > Filters > Manage filters. Check if the TeX (MathJax/QuickLaTeX) or legacy TeX filter is activated
    Affected if TeX filtering is enabled and available to authenticated users
  3. Confirm mimetex renderer is in use
    Check the filter settings at Site administration > Plugins > Filters > TeX notation. Look for the mimetex or legacy LaTeX renderer option being selected
    Affected if Mimetex or legacy TeX renderer is configured as the active rendering method
  4. Check user authentication settings
    Verify that authenticated users have access to the TeX editor functionality. Review roles and capabilities at Site administration > Users > Permissions > Define roles
    Affected if Authenticated (including guest or student) roles can access and submit TeX formulas through the editor
  5. Inspect PHP execution limits
    Check php.ini for max_execution_time and memory_limit settings, or review the Moodle config for $CFG->maxtime or similar timeout configurations
    Affected if No specific timeout limits are configured for the mimetex rendering process

A user is affected if their Moodle version is within the vulnerable ranges AND the TeX filter with mimetex is enabled for authenticated users without strict execution timeouts configured.

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 4.5.9 / 5.0.5 / 5.1.2 or later
Fixed in 4.5.95.0.55.1.2
Interim mitigation

Implement proper execution timeouts and resource limits for mimetex TeX rendering, or update to a patched version of Moodle that addresses the insufficient time limits.

Recommended fix High confidence

Moodle 5.1.2 (or latest 5.1.x), alternatively 4.5.9 or 5.0.5 depending on your branch

  1. 1. Back up your current Moodle database and file storage.
  2. 2. Put your Moodle site into maintenance mode via Site Administration > Server > Maintenance Mode.
  3. 3. Download the appropriate Moodle version based on your current branch: 4.5.9 for 4.x users, 5.0.5 for 5.0.x users, or 5.1.2 for 5.1.x users.
  4. 4. Extract the new Moodle files to your server, replacing the old installation.
  5. 5. Run the Moodle upgrade script by accessing your site URL (or CLI: php admin/cli/upgrade.php).
  6. 6. Verify the upgrade completed successfully and test TeX formula rendering.
  7. 7. Disable maintenance mode via Site Administration > Server > Maintenance Mode.
Caveat Standard Moodle upgrade precautions apply - review plugin compatibility and test in staging first

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

Fix this in Moodle Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.

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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-2026-26047 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