CVE-2021-36403

MEDIUMNVD 5.35.3—

5.3

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.

CVSS v3: 5.3
EG Score: 5.3(medium)
EPSS: 53.3%
KEV: Not listed

Published

March 6, 2023

Last Modified

March 7, 2025

References (2)

patrick@puiterwijkhttps://moodle.org/mod/forum/discuss.php?d=424809
af854a3a-2127-422b-91ae-364da2661108https://moodle.org/mod/forum/discuss.php?d=424809

Affected Packages

(1 across 1 ecosystem)

Packagist(1)

Package	Vulnerable range	Fixed in	Dependents
moodle/moodle	v2.3.10 ... v3.9.7 (255 versions)	3.9.8	—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

CWE-912

Data Freshness Timeline

(refreshed 12× in last 7d / 20× in last 30d)

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-06-02 20:11 UTCepss_batch
2026-06-02 20:11 UTCepss_batch
2026-06-01 13:50 UTCepss_batch
2026-06-01 13:50 UTCepss_batch
2026-05-31 22:29 UTCepss_batch
2026-05-31 22:29 UTCepss_batch
2026-05-31 00:15 UTCepss_batch
2026-05-31 00:15 UTCepss_batch
2026-05-29 13:42 UTCepss_batch
2026-05-29 13:42 UTCepss_batch
2026-05-28 13:43 UTCepss_batch
2026-05-28 13:43 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-25 05:42 UTCEG score recompute

Frequently asked(5)

What is CVE-2021-36403?

CVE-2021-36403 is a medium vulnerability published on March 6, 2023. 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.

When was CVE-2021-36403 disclosed?

CVE-2021-36403 was first published in the National Vulnerability Database on March 6, 2023, with the most recent update on March 7, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2021-36403 actively exploited?

CVE-2021-36403 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 53.3% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-36403?

CVE-2021-36403 has a CVSS v3 base score of 5.3 (NVD).

How do I remediate CVE-2021-36403?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-36403, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2021-36403

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Is Your Infrastructure Affected by CVE-2021-36403?

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