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Critical, CVSS 9.8

Moodle vulnerable to RCE via unsafe deserialization

CVE-2021-3943GHSA-8jhp-2gcr-qw96

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (moodle/moodle 3.11.4, 3.10.8, 3.9.11), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • Packagist moodle/moodle

    Affected
    >= 3.11, <= 3.11.3>= 3.10, <= 3.10.7>= 3.9, <= 3.9.10
    Fixed in
    3.10.8, 3.9.11, 3.11.4

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
9.8 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
  • CVE-2021-3943: 2.40% estimated exploitation activity in the next 30 days; percentile 84.01 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

A flaw was found in Moodle in versions 3.11 to 3.11.3, 3.10 to 3.10.7, 3.9 to 3.9.10 and earlier unsupported versions. A remote code execution risk when restoring backup files was identified.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-8jhp-2gcr-qw96

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2021-3943

Advisory: Moodle vulnerable to RCE via unsafe deserialization
IDs: CVE-2021-3943, GHSA-8jhp-2gcr-qw96
Record: https://patchnext.com/advisories/cve-2021-3943 (revision 1, source checked 26 Oct 2026, 14:06 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: moodle/moodle 3.11.4, 3.10.8, 3.9.11. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist moodle/moodle: affected >= 3.11, <= 3.11.3; >= 3.10, <= 3.10.7; >= 3.9, <= 3.9.10; fixed in 3.10.8, 3.9.11, 3.11.4

## Suggested inspection (read-only)
- Packagist moodle/moodle: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on moodle/moodle.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-8jhp-2gcr-qw96 (GitHub-reviewed advisory GHSA-8jhp-2gcr-qw96 lists affected ranges: Packagist moodle/moodle >=3.11 =3.10 =3.9 <=3.9.10)

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