CVE-2021-40694Network attack vector

Arbitrary file read via unescaped LaTeX preamble

Published Jan 21, 2022 · Updated Aug 4, 2024

Improper output escaping in Moodle LMS allows remote authenticated users with site-admin rights to read files accessible to the HTTP server account. The TeX filter accepts a configurable LaTeX preamble without adequately escaping file-inclusion syntax before passing it to the renderer. Exploitation requires control of the site-administrator setting, and disclosure is limited to files readable by the web-server account.

CVSS severity4.9
Medium
EPSS probability0.90%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper output escaping in Moodle LMS allows remote authenticated users with site-admin rights to read files accessible to the HTTP server account. The TeX filter accepts a configurable LaTeX preamble without adequately escaping file-inclusion syntax before passing it to the renderer. Exploitation requires control of the site-administrator setting, and disclosure is limited to files readable by the web-server account.

The record

CVE
CVE-2021-40694
Published
Jan 21, 2022
Updated
Aug 4, 2024
Vendor
Moodle
Product
Moodle LMS
Classifications
CWE-116, T1005
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Jan 21, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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=3.11 to 3.11.2, 3.10 to 3.10.6, 3.9 to 3.9.9 and earlier unsupported versions

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Moodle · Moodle LMSversion=3.11 to 3.11.2, 3.10 to 3.10.6, 3.9 to 3.9.9 and earlier unsupported versions

Published CVSS scores

4.9UbuntuCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N

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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-116Improper Encoding or Escaping of Output
T1005Data from Local System

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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