How severe is CVE-2021-3943?

CVE-2021-3943 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-3943 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (82nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3943?

CVE-2021-3943 affects Moodle. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-3943?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-3943 published?

CVE-2021-3943 was published on 2021-11-22 and last updated on 2026-06-17.

CVE-2021-3943

CVE-2021-3943 is a critical-severity vulnerability in Moodle with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-20.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (82nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Moodle
Published: 2021-11-22
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is 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.
How severe is CVE-2021-3943?: CVE-2021-3943 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-3943 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (82nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3943?: CVE-2021-3943 affects Moodle. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-3943?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-3943 published?: CVE-2021-3943 was published on 2021-11-22 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:moodle:moodle:*:*:*:*:*:*:*:*

More vulnerabilities in Moodle

CVE-2006-4935 — Critical (CVSS 10.0): The Database module in Moodle before 1.6.2 does not properly handle uploaded files, which has unspecified impact and…
CVE-2006-4936 — Critical (CVSS 10.0): Moodle before 1.6.2 does not properly validate the module instance id when creating a course module object, which has…
CVE-2005-2247 — Critical (CVSS 10.0): Multiple unknown vulnerabilities in Moodle before 1.5.1 have unknown impact and attack vectors.
CVE-2004-2233 — Critical (CVSS 10.0): Unknown "front page vulnerability with Moodle servers" for Moodle before 1.3.2 has unknown impact and attack vectors.
CVE-2004-2236 — Critical (CVSS 10.0): Unknown vulnerability in Moodle before 1.3.3 has unknown impact and attack vectors, related to language setting.
CVE-2004-2237 — Critical (CVSS 10.0): Unknown vulnerability in Moodle before 1.3.4 has unknown impact and attack vectors, related to "strings in Moodle…

All CVEs affecting Moodle →

Other CWE-20 (Improper Input Validation) vulnerabilities

CVE-2026-48316 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Improper Input Validation vulnerability that could…
CVE-2026-48281 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Improper Input Validation vulnerability that could…
CVE-2026-48277 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Improper Input Validation vulnerability that could…
CVE-2026-48055 — Critical (CVSS 10.0): Streambert is a cross-platform Electron Desktop App to stream and download any video media. In versions 2.4.0 and…
CVE-2026-34910 — Critical (CVSS 10.0): A malicious actor with access to the network could exploit an Improper Input Validation vulnerability found in UniFi OS…
CVE-2026-33587 — Critical (CVSS 10.0): Lack of user input sanitisation in Open Notebook v1.8.3 allows the application user to execute Python code (and…

Browse all CWE-20 (Improper Input Validation) vulnerabilities →