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Fencer Vulns
critical 9.8

CVE-2021-3943 json

Moodle vulnerable to RCE via unsafe deserialization

published 2021-11-22 4 y ago modified 2026-09-08 2 mo ago also BIT-moodle-2021-3943 , EUVD-2021-2325 , GHSA-8jhp-2gcr-qw96

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.4%
EPSS 2.4% chance of exploitation in 30 days, percentile 84%
public exploits
0
none known

Summary

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.

Patch / fix

  • packagist moodle/moodle 3.9.11, 3.10.8, 3.11.4
  • bitnami moodle 3.9.11, 3.10.8, 3.11.4

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-3943 updated

moodle: remote code execution risk when restoring malformed backup file

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.40% chance of exploitation in the next 30 days, higher than 84% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
GitHub 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P
OSV 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
packagist moodle/moodle
>=3.11, <3.11.4
>=3.10, <3.10.8
>=3.9, <3.9.11
3.11.4
3.10.8
3.9.11
bitnami moodle
>=3.9.0, <3.9.11
>=3.10.0, <3.10.8
>=3.11.0, <3.11.4
3.9.11
3.10.8
3.11.4

Affected products

  • n/a moodle

Classification

Weakness
  • CWE-20 Improper Input Validation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.