CVE-2021-36399

Moodle Cross-site Scripting vulnerability

5.4 MediumFix available

In Moodle, ID numbers displayed in the quiz override screens required additional sanitizing to prevent a stored XSS risk.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: Low
User interaction: Required

What an attacker can affect

Confidentiality: Low
Integrity: Low
Availability: None

Exploit likelihood

0.52%Up 0.5 points since Mar 7, 2023

What each source reports

NVD Score used 5.4

In Moodle, ID numbers displayed in the quiz override screens required additional sanitizing to prevent a stored XSS risk.

Record: CVE-2021-36399
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Weakness: CWE-79
Updated: 2026-11-02

CVE List 5.4

In Moodle, ID numbers displayed in the quiz override screens required additional sanitizing to prevent a stored XSS risk.

Record: CVE-2021-36399
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Weakness: CWE-79
Updated: 2026-11-02

EUVDEUVD-2023-0921 5.4

In Moodle, ID numbers displayed in the quiz override screens required additional sanitizing to prevent a stored XSS risk.

Record: EUVD-2023-0921
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Updated: 2026-11-02

GitHub AdvisoriesGHSA-79jp-m64f-pgrc 5.4

Moodle Cross-site Scripting vulnerability

In Moodle, ID numbers displayed in the quiz override screens required additional sanitizing to prevent a stored XSS risk.

Record: GHSA-79jp-m64f-pgrc
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Weakness: CWE-79
Updated: 2026-11-02

OSV 5.4

In Moodle, ID numbers displayed in the quiz override screens required additional sanitizing to prevent a stored XSS risk.

Record: CVE-2021-36399
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Updated: 2026-11-02

OSVGHSA-79jp-m64f-pgrc 5.4

Moodle Cross-site Scripting vulnerability

In Moodle, ID numbers displayed in the quiz override screens required additional sanitizing to prevent a stored XSS risk.

Record: GHSA-79jp-m64f-pgrc
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Weakness: CWE-79
Updated: 2026-11-02

OSVUBUNTU-CVE-2021-36399 5.4

In Moodle, ID numbers displayed in the quiz override screens required additional sanitizing to prevent a stored XSS risk.

Record: UBUNTU-CVE-2021-36399
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Updated: 2026-11-02

OSVBIT-moodle-2021-36399 No score

In Moodle, ID numbers displayed in the quiz override screens required additional sanitizing to prevent a stored XSS risk.

Record: BIT-moodle-2021-36399
Updated: 2026-11-02

Affected products

moodle

Affected packages

Affected packages
Package	Affected	Fixed
`moodle/moodle` Packagist	3.11.0-beta up to 3.11.1	3.11.1
`moodle/moodle` Packagist	3.10.0-beta up to 3.10.5	3.10.5
`moodle/moodle` Packagist	before 3.9.8	3.9.8
`moodle` Bitnami	3.11.0 up to 3.11.1	3.11.1
`moodle/moodle` Packagist	3.11.0-beta up to 3.11.1, plus listed versions v3.11.0v3.11.0-betav3.11.0-rc1v3.11.0-rc2	3.11.1
`moodle/moodle` Packagist	3.10.0-beta up to 3.10.5, plus listed versions v3.10.0v3.10.0-betav3.10.0-rc1v3.10.0-rc2v3.10.1v3.10.2v3.10.3v3.10.4	3.10.5
`moodle/moodle` Packagist	before 3.9.8, plus listed versions v2.3.10v2.3.11v2.3.4v2.3.5v2.3.6 Show 45 moreShow less v2.3.7v2.3.8v2.3.9v2.4.0v2.4.0-rc1v2.4.1v2.4.10v2.4.11v2.4.2v2.4.3v2.4.4v2.4.5v2.4.6v2.4.7v2.4.8v2.4.9v2.5.0v2.5.0-betav2.5.0-rc1v2.5.1v2.5.2v2.5.3v2.5.4v2.5.5v2.5.6v2.5.7v2.5.8v2.5.9v2.6.0v2.6.0-betav2.6.0-rc1v2.6.1v2.6.10v2.6.11v2.6.2v2.6.3v2.6.4v2.6.5v2.6.6v2.6.7v2.6.8v2.6.9v2.7.0v2.7.0-betav2.7.0-rc1	3.9.8
`moodle` Ubuntu: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
`moodle` Ubuntu:Pro:18.04:LTS	All versions, plus listed versions 3.0.3+dfsg-0ubuntu13.0.3+dfsg-0ubuntu1+esm1	None known

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-36399 is a medium vulnerability (CVSS 5.4) in Moodle, published March 6, 2023. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.52%, the 44th percentile. Fixed in moodle/moodle 3.11.1.

References

This page doesn't list everything

Left out here: 205 versions. The JSON record has them.