CVE-2021-36394: Moodle/moodle Moodle Session Fixation Vulnerability Vulnerability

CRITICAL
Advisory Identifier: GHSA-2563-fp9c-mgm8
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CVSS 9.8
CWE-384 CWE-94
Published
Advisory Summary

CVE-2021-36394 is a CRITICAL (CVSS 9.8) moodle session fixation vulnerability vulnerability (CWE-384: Session Fixation) affecting Moodle/moodle libraries in the Packagist ecosystem. The issue involves moodle session fixation vulnerability. Remediation is available by upgrading affected packages to version 3.11.1, 3.10.5, 3.9.8.

CVE-2021-36394 at a Glance

CVE Identifier CVE-2021-36394
GHSA Identifier GHSA-2563-fp9c-mgm8
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-384: Session Fixation
Affected Product Moodle/moodle
Package Ecosystem Packagist
Published Date
Last Updated

Security Impact

CVSS: 9.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2021-36394

To remediate this vulnerability, upgrade all affected Moodle/moodle dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

moodle/moodle fixed: 3.11.1 
Upgrade moodle/moodle to 3.11.1
moodle/moodle fixed: 3.10.5 
Upgrade moodle/moodle to 3.10.5
moodle/moodle fixed: 3.9.8 
Upgrade moodle/moodle to 3.9.8
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for moodle/moodle

How to Check if You Are Affected

To determine whether your application is affected by CVE-2021-36394, inspect your project dependencies for Moodle/moodle:

inspect dependencies for moodle/moodle

Analyze the terminal output to locate any version of Moodle/moodle in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.11.1), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-384: Session Fixation, where authenticating a user, or otherwise establishing a new user session, without invalidating any existing session identifier gives an attacker the opportunity to steal authenticated sessions. In Moodle/moodle, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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

CVE-2021-36394 Affected Moodle/moodle Versions

3 component(s)
Fixed Versions:
3.11.13.10.53.9.8
Product / Package Ecosystem Affected Versions Fixed Version
moodle/moodle
 Packagist
≥ 3.11.0-beta
< 3.11.1
3.11.1
moodle/moodle
 Packagist
≥ 3.10.0-beta
< 3.10.5
3.10.5
moodle/moodle
 Packagist
< 3.9.8
3.9.8

References

NVD — CVE-2021-36394 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-36394
Moodle/moodle Source Repository REPOSITORY
https://github.com/moodle/moodle
moodle.org/mod/forum/discuss.p... WEB
https://moodle.org/mod/forum/discuss.php?d=424799

Frequently Asked Questions

What is CVE-2021-36394?
CVE-2021-36394 is a security vulnerability in Moodle/moodle involving Moodle Session Fixation vulnerability under CWE-384: Session Fixation.
Which Moodle/moodle versions are affected?
Affected versions include releases prior to 3.11.1, 3.10.5, 3.9.8 across affected packages: moodle/moodle.
What version fixes CVE-2021-36394?
Upgrading to 3.11.1, 3.10.5, 3.9.8 (or the latest patched release for your respective branch) resolves the vulnerability.
Is moodle/moodle affected?
Yes, moodle/moodle is affected in releases prior to 3.11.1, 3.10.5, 3.9.8. Upgrade your dependency to 3.11.1, 3.10.5, 3.9.8 or later.
What is the CVSS score of CVE-2021-36394?
CVE-2021-36394 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2021-36394?
CVE-2021-36394 is classified under CWE-384: Session Fixation (Authenticating a user, or otherwise establishing a new user session, without invalidating any existing session identifier gives an attacker the opportunity to steal authenticated sessions.).
How can I check Packagist dependencies for CVE-2021-36394?
Run the dependency tree command: 'inspect dependencies for moodle/moodle'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-2563-fp9c-mgm8",
  "modified" : "2025-03-06T20:57:35Z",
  "published" : "2023-03-06T21:30:18Z",
  "aliases" : [ "CVE-2021-36394" ],
  "summary" : "Moodle Session Fixation vulnerability",
  "details" : "In Moodle, a remote code execution risk was identified in the Shibboleth authentication plugin.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "moodle/moodle"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.11.0-beta"
      }, {
        "fixed" : "3.11.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "moodle/moodle"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.10.0-beta"
      }, {
        "fixed" : "3.10.5"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "moodle/moodle"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.9.8"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-36394"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/moodle/moodle"
  }, {
    "type" : "WEB",
    "url" : "https://moodle.org/mod/forum/discuss.php?d=424799"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-384", "CWE-94" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2023-03-07T20:59:15Z",
    "nvd_published_at" : "2023-03-06T21:15:00Z"
  }
}