Cyber Resilience

CVE-2021-20185

Medium

Published: 28 January 2021

Published
28 January 2021
Modified
21 November 2024
KEV Added
Patch
CVSS Score v3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
EPSS Score 0.0038 60.0th percentile
Risk Priority 11 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2021-20185 is a medium-severity Uncontrolled Resource Consumption (CWE-400) vulnerability in Moodle Moodle. Its CVSS base score is 5.3 (Medium).

Operationally, ranked in the top 40.0% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability details

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.

CWE(s)

Related Threats

No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.

Affected Assets

moodle
moodle
3.10.0 · 3.5.0 — 3.5.16 · 3.8.0 — 3.8.7 · 3.9.0 — 3.9.4

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

addresses: CWE-400 CWE-770

Limiting concurrent sessions directly prevents uncontrolled resource consumption by capping the number of active sessions per user or account.

addresses: CWE-400 CWE-770

Contingency plan testing includes resource exhaustion scenarios to verify recovery, making it harder for attackers to sustain exploits that cause uncontrolled consumption.

addresses: CWE-400 CWE-770

Updated contingency plans include current procedures to detect, contain, and recover from resource exhaustion, limiting an attacker's ability to sustain impact from uncontrolled consumption.

addresses: CWE-400 CWE-770

Alternate site allows resumption of operations if resource exhaustion at the primary site is exploited to cause unavailability.

addresses: CWE-400 CWE-770

Alternate telecommunications services enable resumption of essential functions when primary services become unavailable due to uncontrolled resource consumption.

addresses: CWE-400 CWE-770

Planning and coordination of security activities (scans, tests, maintenance) directly imposes scheduling and throttling that prevents those activities from producing uncontrolled resource consumption.

addresses: CWE-400 CWE-770

Performance metrics and monitoring inherently track resource consumption patterns, making uncontrolled consumption easier to detect and mitigate.

addresses: CWE-400 CWE-770

Terminating idle connections bounds resource consumption that would otherwise allow uncontrolled accumulation of open sessions.

References