CVE-2021-43558Network attack vector

Reflected XSS via unsanitized filetype URL parameter

Published Nov 22, 2021 · Updated Aug 4, 2024

Reflected XSS in Moodle LMS 3.11 through 3.11.3, 3.10 through 3.10.7, and 3.9 through 3.9.10 allows remote attackers to run script. The filetype site-administration tool reflects a URL parameter into generated HTML without the additional sanitization needed to neutralize script markup. The attacker needs no Moodle account, but a site administrator must open the crafted URL; successful execution can read or alter browser-accessible data in the administrator's session.

CVSS severity6.1
Medium
EPSS probability0.87%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Reflected XSS in Moodle LMS 3.11 through 3.11.3, 3.10 through 3.10.7, and 3.9 through 3.9.10 allows remote attackers to run script. The filetype site-administration tool reflects a URL parameter into generated HTML without the additional sanitization needed to neutralize script markup. The attacker needs no Moodle account, but a site administrator must open the crafted URL; successful execution can read or alter browser-accessible data in the administrator's session.

The record

CVE
CVE-2021-43558
Published
Nov 22, 2021
Updated
Aug 4, 2024
Vendor
Moodle
Product
Moodle LMS
Classifications
CWE-79, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 22, 2021CVE 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=moodle 3.11.4, moodle 3.10.8 and moodle 3.9.11

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Moodle · Moodle LMSversion=moodle 3.11.4, moodle 3.10.8 and moodle 3.9.11

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1189Drive-by Compromise

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo