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MoodleCMS

CVE-2023-35133

HIGH · 7.5 CVSS v3.1 Published 2023-06-22
Fix available
A fix is available. Upgrade to 3.9.22 / 3.11.15 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click Patch available

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
An issue in the logic used to check 0.0.0.0 against the cURL blocked hosts lists resulted in an SSRF risk. This flaw affects Moodle versions 4.2, 4.1 to 4.1.3, 4.0 to 4.0.8, 3.11 to 3.11.14, 3.9 to 3.9.21 and earlier unsupported versions.

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
How this class of weakness works · CWE-918

The server can be induced to make requests to a URL an attacker controls, turning it into a proxy into internal networks and cloud metadata services. It's especially dangerous behind a trusted network boundary. The fix is strict allow-listing of destinations and blocking access to internal address ranges.

General guidance for the server-side request forgery (ssrf) class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

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:< 3.9.22>= 3.11.0, < 3.11.15>= 4.0.0, < 4.0.9>= 4.1.0, < 4.1.4= 4.2.0

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

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 3.9.22 / 3.11.15 / 4.0.9 or later
Fixed in 3.9.223.11.154.0.9
Vendor patch moodle.org →
Recommended fix High confidence

Moodle 3.9.22, 3.11.15, 4.0.9, 4.1.4, or 4.2.1+ (depending on which major version branch you are on)

  1. 1. Identify the currently installed Moodle version using the admin interface (Site administration > Server > Environment) or by checking the version.php file in the Moodle root directory
  2. 2. Determine which upgrade path applies based on your current version: for 3.9.x upgrade to 3.9.22, for 3.11.x upgrade to 3.11.15, for 4.0.x upgrade to 4.0.9, for 4.1.x upgrade to 4.1.4, for 4.2.x upgrade to 4.2.1 or later
  3. 3. Back up the Moodle database and the entire Moodle directory (including moodledata) before proceeding
  4. 4. Download the appropriate target version from https://download.moodle.org/releases/
  5. 5. Replace the Moodle source files with the new version, preserving config.php and any custom modifications
  6. 6. Run the upgrade script by accessing the site URL (e.g., https://yourmoodle.example.com) which will trigger the upgrade process
  7. 7. Verify successful upgrade by logging in and checking the version in Site administration > Server > Environment
  8. 8. Test that the cURL blocked hosts functionality works correctly to confirm the SSRF fix is applied
Caveat Standard Moodle upgrades may require PHP version compatibility checks; review Moodle's compatibility matrix before upgrading; always test in a staging environment first

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

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $3,200. Get the upgrade done

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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-2023-35133 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