How severe is CVE-2021-20185?

CVE-2021-20185 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2021-20185 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (69th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-20185?

CVE-2021-20185 primarily affects Moodle. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-20185?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-20185 published?

CVE-2021-20185 was published on 2021-01-28 and last updated on 2026-06-17.

CVE-2021-20185

CVE-2021-20185 is a medium-severity vulnerability in Moodle with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-770.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
CVSS v2: 5.0
EPSS exploit prediction: 1% (69th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-770
Affected product: Moodle
Published: 2021-01-28
Last modified: 2026-06-17

Description

It was found in Moodle before version 3.10.1, 3.9.4, 3.8.7 and 3.5.16 that messaging did not impose a character limit when sending messages, which could result in client-side (browser) denial of service for users receiving very large messages.

Frequently asked questions

What is CVE-2021-20185?: It was found in Moodle before version 3.10.1, 3.9.4, 3.8.7 and 3.5.16 that messaging did not impose a character limit when sending messages, which could result in client-side (browser) denial of service for users receiving very large messages.
How severe is CVE-2021-20185?: CVE-2021-20185 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2021-20185 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (69th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-20185?: CVE-2021-20185 primarily affects Moodle. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-20185?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-20185 published?: CVE-2021-20185 was published on 2021-01-28 and last updated on 2026-06-17.

References

https://moodle.org/mod/forum/discuss.php?d=417168

Affected products (2)

cpe:2.3:a:moodle:moodle:*:*:*:*:*:*:*:*
cpe:2.3:a:moodle:moodle:3.10.0:*:*:*:*:*:*:*

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