CVE-2021-36394Public exploitNetwork attack vector

Unauthenticated code execution via session deserialization

Published Mar 6, 2023 · Updated Mar 6, 2025

Code injection in Moodle LMS 3.11, 3.10 through 3.10.4, and 3.9.7 and earlier allows remote attackers to execute PHP code. The Shibboleth logout helper splits attacker-influenced session data and passes extracted values to PHP unserialize without restricting object classes. The Shibboleth plugin must be enabled; an anonymous session cookie can supply a gadget chain that alters server data or executes code.

CVSS severity9.8
Critical
EPSS probability7.03%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Code injection in Moodle LMS 3.11, 3.10 through 3.10.4, and 3.9.7 and earlier allows remote attackers to execute PHP code. The Shibboleth logout helper splits attacker-influenced session data and passes extracted values to PHP unserialize without restricting object classes. The Shibboleth plugin must be enabled; an anonymous session cookie can supply a gadget chain that alters server data or executes code.

The record

CVE
CVE-2021-36394
Published
Mar 6, 2023
Updated
Mar 6, 2025
Vendor
Moodle
Product
Moodle LMS
Classifications
CWE-94, CWE-384, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 6, 2023CVE publishedPublication date reported by the CVE source.
  2. Mar 6, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.11, 3.10 to 3.10.4, 3.9 to 3.9.7 and earlier unsupported versions

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Moodle · Moodle LMSversion=3.11, 3.10 to 3.10.4, 3.9 to 3.9.7 and earlier unsupported versions

Published CVSS scores

9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-94Improper Control of Generation of Code ('Code Injection')
CWE-384Session Fixation
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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