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Authorization Bypass (IDOR)Weakness · CWE-639

CVE-2026-30884

CRITICAL · 9.6 CVSS v3.1 Published 2026-03-18
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable 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
mdjnelson/moodle-mod_customcert is a Moodle plugin for creating dynamically generated certificates with complete customization via the web browser. Prior to versions 4.4.9 and 5.0.3, a teacher who holds `mod/customcert:manage` in any single course can read and silently overwrite certificate elements belonging to any other course in the Moodle installation. The `core_get_fragment` callback `editelement` and the `mod_customcert_save_element` web service both fail to verify that the supplied `elementid` belongs to the authorized context, enabling cross-course information disclosure and data tampering. Versions 4.4.9 and 5.0.3 fix the issue.

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-639

The application uses a user-supplied identifier to look up a record without checking that the requester actually owns it, so changing the identifier in a request returns someone else's data. This is the classic insecure-direct-object-reference — the change-the-ID-in-the-URL bug. Remediation is authorizing every object access against the acting user, not merely confirming they are logged in.

General guidance for the authorization bypass (idor) class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

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
Changed
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/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
Patch available Apply the vendor patch
Vendor patch github.com →
Recommended fix High confidence

Upgrade to mod_customcert version 4.4.9 (for Moodle 4.1-4.4) or version 5.0.3 (for Moodle 4.5+)

  1. Identify the currently installed version of the mod_customcert plugin in Moodle (usually found in Site Administration > Plugins > Plugins overview or the version.php file in the plugin directory)
  2. Determine which Moodle version is running to select the appropriate customcert plugin version (version 4.4.x for Moodle 4.1-4.4, version 5.0.x for Moodle 4.5+)
  3. Download the fixed version: version 4.4.9 or 5.0.3 from the Moodle Plugins directory or GitHub repository
  4. Create a full backup of the Moodle database and the mod_customcert plugin directory (typically /mod/customcert/)
  5. Navigate to Site Administration > Plugins > Install plugins and upload the new version, OR manually replace the /mod/customcert/ directory files
  6. Run the Moodle upgrade process via CLI (php admin/cli/upgrade.php) or through the web interface to ensure database schema updates are applied
  7. Verify the fix by confirming the new plugin version is reported as 4.4.9 or 5.0.3
Caveat Review the plugin's release notes for any breaking changes between your current version and the fixed version before upgrading

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

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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-2026-30884 in production — separate from our analysis above.

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  • Version or environment caveats, and links to real fixes
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