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Vulnerabilities

Threat intelligence · CVE-2021-36403

In Moodle, in some circumstances, email notifications of messages could have the link back to the original message hidden by HTML, which may pose a phishing risk.

Published Mar 6, 2023 · catalog updated Jun 17, 2026 · In Moodle, in some

Last checked Nov 5, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2021-36403. EPSS is 0.53%. Act only if a listed version of In Moodle, in some is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (In Moodle, in some).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
Medium5.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.53%
Remediation
Version ranges on file
Affected products
cpe moodle/moodle

In Moodle, in some circumstances, email notifications of messages could have the link back to the original message hidden by HTML, which may pose a phishing risk.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe moodle/moodle< 3.10.5
  • cpe moodle/moodle< 3.11.1
  • cpe moodle/moodle< 3.9.8

How to fix CVE-2021-36403

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2021-36403. EPSS is 0.53%. Act only if a listed version of In Moodle, in some is installed.

Which versions are affected?

Compare what you have installed with < 3.10.5, < 3.11.1, < 3.9.8. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-912: Hidden Functionality. EPSS 0.53%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Moodle security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Mar 6, 2023 · Monitored products — high

    Detected

    In Moodle, in some circumstances, email notifications of messages could have the link back to the original message hidden by HTML, which may pose a phishing risk.

  2. Jun 17, 2026 · Monitored products — high

    Updated

    In Moodle, in some circumstances, email notifications of messages could have the link back to the original message hidden by HTML, which may pose a phishing risk.

Sources

  • CVE.orgVulnerability recordCVE-2021-36403

    Official CVE identifier

    cve.org
  • Monitored products — highVendor advisoryCVE-2021-36403

    In Moodle, in some circumstances, email notifications of messages could have the link back to the original message hidden by HTML, which may pose a phishing risk.

    nvd.nist.gov

References

Freshness

Last verified in this catalog Nov 4, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • CVE.orgNov 5, 2026
  • Monitored products — highNov 4, 2026