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Fencer Vulns
medium 5.3

CVE-2021-20185 json

Moodle Client side denial of service via personal message

published 2021-01-28 5 y ago modified 2026-09-08 2 mo ago also BIT-moodle-2021-20185 , EUVD-2022-3488 , GHSA-c3j6-33r4-89q3

cvss
5.3
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.4%
EPSS 1.4% chance of exploitation in 30 days, percentile 72%
public exploits
0
none known

Summary

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.

Patch / fix

  • packagist moodle/moodle 3.5.16, 3.8.7, 3.9.4, 3.10.1
  • bitnami moodle 3.5.16, 3.8.7, 3.9.4, 3.10.1
  • moodle moodle 3.5.16, 3.8.7, 3.9.4

Exploit prediction

1.39% chance of exploitation in the next 30 days, higher than 72% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
GitHub 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
NVD 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P
OSV 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected packages

ecosystem package affected fixed in
packagist moodle/moodle
>=3.5, <3.5.16
>=3.8, <3.8.7
>=3.9, <3.9.4
>=3.10, <3.10.1
3.5.16
3.8.7
3.9.4
3.10.1
bitnami moodle
>=3.5.0, <3.5.16
>=3.8.0, <3.8.7
>=3.9.0, <3.9.4
>=3.10.0, <3.10.1
3.5.16
3.8.7
3.9.4
3.10.1

Affected products

  • n/a moodle

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption
  • CWE-770 Allocation of Resources Without Limits or Throttling

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.