CVE-2021-36394

Moodle Session Fixation vulnerability

9.8 CriticalPublic exploitFix available

In Moodle, a remote code execution risk was identified in the Shibboleth authentication plugin.

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

7.03%Up 7.0 points since Mar 7, 2023

What each source reports

NVD Score used 9.8

In Moodle, a remote code execution risk was identified in the Shibboleth authentication plugin.

Record: CVE-2021-36394
CVSS 3.1: 9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness: CWE-384, CWE-94
Updated: 2026-11-02

CVE List No score

In Moodle, a remote code execution risk was identified in the Shibboleth authentication plugin.

Record: CVE-2021-36394
Weakness: CWE-384, CWE-94
Updated: 2026-11-02

EUVDEUVD-2023-0826 0.0

In Moodle, a remote code execution risk was identified in the Shibboleth authentication plugin.

Record: EUVD-2023-0826
CVSS: 0.0 NoneCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated: 2026-11-02

GitHub AdvisoriesGHSA-2563-fp9c-mgm8 9.8

Moodle Session Fixation vulnerability

In Moodle, a remote code execution risk was identified in the Shibboleth authentication plugin.

Record: GHSA-2563-fp9c-mgm8
CVSS 3.1: 9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness: CWE-94, CWE-384
Updated: 2026-11-02

OSV 9.8

In Moodle, a remote code execution risk was identified in the Shibboleth authentication plugin.

Record: CVE-2021-36394
CVSS 3.1: 9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated: 2026-11-02

OSVGHSA-2563-fp9c-mgm8 9.8

Moodle Session Fixation vulnerability

In Moodle, a remote code execution risk was identified in the Shibboleth authentication plugin.

Record: GHSA-2563-fp9c-mgm8
CVSS 3.1: 9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness: CWE-384, CWE-94
Updated: 2026-11-02

OSVUBUNTU-CVE-2021-36394 9.8

In Moodle, a remote code execution risk was identified in the Shibboleth authentication plugin.

Record: UBUNTU-CVE-2021-36394
CVSS 3.1: 9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated: 2026-11-02

OSVBIT-moodle-2021-36394 No score

In Moodle, a remote code execution risk was identified in the Shibboleth authentication plugin.

Record: BIT-moodle-2021-36394
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	before 3.9.8, 3.10.0 up to 3.10.5, 3.11.0 up to 3.11.1	3.9.83.10.53.11.1
`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

Public exploits

Links only. Every CVE stores no exploit code.

Public exploits
Source	Link	Date
PoC in GitHub	dinhbaouit/CVE-2021-36394	2021-08-28
PoC in GitHub	lavclash75/CVE-2021-36394-Pre-Auth-RCE-in-Moodle	2022-04-26

History

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

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

In short

CVE-2021-36394 is a critical vulnerability (CVSS 9.8) in Moodle, published March 6, 2023. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 7.03%, the 94th 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.