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MoodleCMS

CVE-2021-36396

HIGH · 7.5 CVSS v3.1 Published 2023-03-06
Fix available
A fix is available. Upgrade to 3.9.8 / 3.10.5 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
In Moodle, insufficient redirect handling made it possible to blindly bypass cURL blocked hosts/allowed ports restrictions, resulting in a blind SSRF risk.

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:< 3.9.8>= 3.10.0, < 3.10.5>= 3.11.0, < 3.11.1

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
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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 3.9.8 / 3.10.5 / 3.11.1 or later
Fixed in 3.9.83.10.53.11.1
Vendor patch moodle.org →
Recommended fix High confidence

Moodle 3.9.8 (for 3.9.x) / Moodle 3.10.5 (for 3.10.x) / Moodle 3.11.1 (for 3.11.x)

  1. 1. Identify the currently installed Moodle version in admin > Site administration > Server > System paths or by checking the version.php file in the Moodle root directory.
  2. 2. Determine which upgrade path applies based on current version: if < 3.9.8 upgrade to 3.9.8; if >= 3.10.0 and < 3.10.5 upgrade to 3.10.5; if >= 3.11.0 and < 3.11.1 upgrade to 3.11.1.
  3. 3. Backup the Moodle database and complete Moodle directory before proceeding with upgrade.
  4. 4. Download the appropriate Moodle upgrade package from https://download.moodle.org/releases/
  5. 5. Extract the new Moodle files over the existing installation, preserving config.php and any custom themes or plugins.
  6. 6. Run the Moodle upgrade process by accessing the site URL - the system will automatically detect and run necessary database migrations.
  7. 7. Clear all Moodle caches after upgrade via Site administration > Development > Purge caches.
  8. 8. Verify the upgrade was successful by checking the version number and testing core functionality.
Caveat Standard Moodle minor version upgrades typically have minimal breaking changes, but review the release notes at https://docs.moodle.org/dev/Releases for any behavior changes affecting custom code or plugins.

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-2021-36396 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