CVE-2021-3943
Moodle vulnerable to RCE via unsafe deserialization
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
NVD Score used
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.
- Record
CVE-2021-3943- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - CVSS 2.0
- 7.5 High
AV:N/AC:L/Au:N/C:P/I:P/A:P - Weakness
- CWE-20
- Updated
- 2026-11-02
CVE ListNo score
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.
- Record
CVE-2021-3943- Weakness
- CWE-20
- Updated
- 2026-11-02
EUVDEUVD-2021-2325No score
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.
- Record
EUVD-2021-2325- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-8jhp-2gcr-qw96
Moodle vulnerable to RCE via unsafe deserialization
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.
- Record
GHSA-8jhp-2gcr-qw96- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-20
- Updated
- 2026-11-02
OSV
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.
- Record
CVE-2021-3943- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSVGHSA-8jhp-2gcr-qw96
Moodle vulnerable to RCE via unsafe deserialization
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.
- Record
GHSA-8jhp-2gcr-qw96- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-20
- Updated
- 2026-11-02
OSVUBUNTU-CVE-2021-3943
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.
- Record
UBUNTU-CVE-2021-3943- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSVBIT-moodle-2021-3943No score
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.
- Record
BIT-moodle-2021-3943- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
moodle/moodlePackagist | 3.11 to 3.11.3 | 3.11.4 |
moodle/moodlePackagist | 3.10 to 3.10.7 | 3.10.8 |
moodle/moodlePackagist | 3.9 to 3.9.10 | 3.9.11 |
moodleBitnami | 3.9.0 up to 3.9.11, 3.10.0 up to 3.10.8, 3.11.0 up to 3.11.4 | 3.9.113.10.83.11.4 |
moodle/moodlePackagist | 3.11 up to 3.11.4, plus listed versions v3.11.0v3.11.0-betav3.11.0-rc1v3.11.0-rc2v3.11.1v3.11.2v3.11.3 | 3.11.4 |
moodle/moodlePackagist | 3.10 up to 3.10.8, plus listed versions v3.10.0v3.10.0-betav3.10.0-rc1v3.10.0-rc2v3.10.1 Show 6 moreShow lessv3.10.2v3.10.3v3.10.4v3.10.5v3.10.6v3.10.7 | 3.10.8 |
moodle/moodlePackagist | 3.9 up to 3.9.11, plus listed versions v3.9.0v3.9.0-betav3.9.0-rc1v3.9.0-rc2v3.9.0-rc3 Show 10 moreShow lessv3.9.1v3.9.10v3.9.2v3.9.3v3.9.4v3.9.5v3.9.6v3.9.7v3.9.8v3.9.9 | 3.9.11 |
moodleUbuntu:Pro:16.04:LTS | All versions, plus listed versions 2.7.9+dfsg-12.7.10+dfsg-12.7.11+dfsg-12.7.11+dfsg-22.7.12+dfsg-13.0.3+dfsg-0ubuntu13.0.3+dfsg-0ubuntu1+esm1 | None known |
moodleUbuntu:Pro:18.04:LTS | All versions, plus listed versions 3.0.3+dfsg-0ubuntu13.0.3+dfsg-0ubuntu1+esm1 | None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-3943 is a critical vulnerability (CVSS 9.8) in Moodle, published November 22, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 2.40%, the 84th percentile. Fixed in moodle/moodle 3.11.4.
References
bugzilla.redhat.com/show_bug.cgi?id=2021963
moodle.org/mod/forum/discuss.php?d=429095
nvd.nist.gov/vuln/detail/CVE-2021-3943
github.com/moodle/moodle/commit/58e8ad852f9e75c8158e5bee02c273383f7d9865
ubuntu.com/security/CVE-2021-3943
cve.org/CVERecord?id=CVE-2021-3943