CVE-2023-5539Network attack vector

Authenticated code execution via unsafe Lesson deserialization

Published Nov 9, 2023 · Updated Sep 3, 2024

Code injection in affected Moodle LMS releases allows remote authenticated users to execute code through the Lesson activity. Lesson grading, dependency, form, and essay paths passed stored user-controlled data to PHP unserialize(), allowing attacker-supplied objects to be instantiated. Teacher or manager privileges are required by default, and successful exploitation executes code in the server-side Moodle context.

CVSS severity8.8
High
EPSS probability1.86%
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 affected Moodle LMS releases allows remote authenticated users to execute code through the Lesson activity. Lesson grading, dependency, form, and essay paths passed stored user-controlled data to PHP unserialize(), allowing attacker-supplied objects to be instantiated. Teacher or manager privileges are required by default, and successful exploitation executes code in the server-side Moodle context.

The record

CVE
CVE-2023-5539
Published
Nov 9, 2023
Updated
Sep 3, 2024
Vendor
Moodle
Product
Moodle LMS
Classifications
CWE-94, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 9, 2023CVE publishedPublication date reported by the CVE source.
  2. Sep 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=0 <3.9.24
  2. Affected versionversion=3.11.0 <3.11.17
  3. Affected versionversion=4.0.0 <4.0.11
  4. Affected versionversion=4.1.0 <4.1.6
  5. Affected versionversion=4.2.0 <4.2.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Moodle · Moodle LMSversion=0 <3.9.24; version=3.11.0 <3.11.17; version=4.0.0 <4.0.11; version=4.1.0 <4.1.6; version=4.2.0 <4.2.3

Published CVSS scores

4.7Fedora ProjectCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:L
8.8NVDCVSS:3.1/AV:N/AC:L/PR:L/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

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

Public exploit references

No public exploit references are available in this record.

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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