CVE-2021-21809

CRITICALNVD 9.19.1—
EchelonGraph scoreMEDIUM confidence

Score 9.1 from GitHub Security Advisory (severity: CRITICAL) published 2022-05-24. NVD baseline CVSS 9.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 3 sources updated this weekWeaponized
9.1
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 24%CVSS: 9.1Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

A command execution vulnerability exists in the default legacy spellchecker plugin in Moodle 3.10. A specially crafted series of HTTP requests can lead to command execution. An attacker must have administrator privileges to exploit this vulnerabilities.

CVSS v3
9.1
EG Score
9.1(medium)
EG Risk
71(Track*)
EG Risk 71/100SSVC: Track*

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity91% × 45%
Exploitation65% × 40%
Automatability30% × 15%
Action: Watch closely — could escalate to Attend.
EPSS
97.6%
KEV
Not listed

Published

June 23, 2021

Last Modified

November 21, 2024

Advisory Details (2)

Auto-updated Jul 23, 2026
No patch confirmed yet.
generic

TALOS-2021-1277 || Cisco Talos Intelligence Group - Comprehensive Threat Intelligence

https://talosintelligence.com/vulnerability_reports/TALOS-2021-1277
generic

Packet Storm Security

http://packetstormsecurity.com/files/164481/Moodle-SpellChecker-Path-Authenticated-Remote-Command-Execution.html

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
composermoodle/moodle—ghsa

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(1 across 1 ecosystem)
Packagist(1)
PackageVulnerable rangeFixed inDependents
moodle/moodle3.8.0——

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 43× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-23 14:15 UTCEPSS rescore
  2. 2026-07-23 01:57 UTCEG score recompute
  3. 2026-07-22 22:43 UTCEG score recompute
  4. 2026-07-22 14:05 UTCEPSS rescore
  5. 2026-07-21 15:22 UTCEPSS rescore
  6. 2026-07-21 15:22 UTCEPSS rescore
  7. 2026-07-20 17:04 UTCEPSS rescore
  8. 2026-07-19 14:28 UTCEPSS rescore
  9. 2026-07-19 02:26 UTCEPSS rescore
  10. 2026-07-18 17:59 UTCOSV refresh
  11. 2026-07-18 10:02 UTCEPSS rescore
  12. 2026-07-16 17:00 UTCEPSS rescore
  13. 2026-07-15 16:55 UTCEPSS rescore
  14. 2026-07-15 16:55 UTCEPSS rescore
  15. 2026-07-13 22:27 UTCEPSS rescore
  16. 2026-07-13 22:27 UTCEPSS rescore
  17. 2026-07-13 06:10 UTCEPSS rescore
  18. 2026-07-13 06:10 UTCEPSS rescore
  19. 2026-07-12 05:44 UTCEPSS rescore
  20. 2026-07-12 05:44 UTCEPSS rescore
  21. 2026-07-11 08:25 UTCEPSS rescore
  22. 2026-07-09 19:07 UTCEPSS rescore
  23. 2026-07-08 15:12 UTCEPSS rescore
  24. 2026-07-07 13:43 UTCEPSS rescore
  25. 2026-07-06 02:21 UTCEPSS rescore
Show 64 more
  1. 2026-07-06 02:21 UTCEPSS rescore
  2. 2026-07-05 02:28 UTCEPSS rescore
  3. 2026-07-05 02:28 UTCEPSS rescore
  4. 2026-07-04 06:29 UTCEPSS rescore
  5. 2026-07-04 06:29 UTCEPSS rescore
  6. 2026-07-02 16:57 UTCEPSS rescore
  7. 2026-07-01 15:03 UTCEPSS rescore
  8. 2026-07-01 00:48 UTCOSV refresh
  9. 2026-06-30 23:20 UTCEPSS rescore
  10. 2026-06-30 23:20 UTCEPSS rescore
  11. 2026-06-28 04:54 UTCEPSS rescore
  12. 2026-06-28 04:54 UTCEPSS rescore
  13. 2026-06-27 03:06 UTCEPSS rescore
  14. 2026-06-27 03:06 UTCEPSS rescore
  15. 2026-06-25 13:48 UTCEPSS rescore
  16. 2026-06-25 13:48 UTCEPSS rescore
  17. 2026-06-24 14:03 UTCEPSS rescore
  18. 2026-06-24 14:03 UTCEPSS rescore
  19. 2026-06-23 21:31 UTCEPSS rescore
  20. 2026-06-23 21:31 UTCEPSS rescore
  21. 2026-06-22 14:24 UTCEPSS rescore
  22. 2026-06-22 14:23 UTCEPSS rescore
  23. 2026-06-21 01:58 UTCEPSS rescore
  24. 2026-06-21 01:57 UTCEPSS rescore
  25. 2026-06-18 17:51 UTCEPSS rescore
  26. 2026-06-18 17:51 UTCEPSS rescore
  27. 2026-06-17 17:51 UTCEPSS rescore
  28. 2026-06-16 17:50 UTCEPSS rescore
  29. 2026-06-15 17:46 UTCEPSS rescore
  30. 2026-06-14 23:15 UTCEPSS rescore
  31. 2026-06-13 22:58 UTCEPSS rescore
  32. 2026-06-13 03:08 UTCOSV refresh
  33. 2026-06-12 23:10 UTCEPSS rescore
  34. 2026-06-12 23:10 UTCEPSS rescore
  35. 2026-06-11 13:58 UTCEPSS rescore
  36. 2026-06-10 22:16 UTCEPSS rescore
  37. 2026-06-10 22:16 UTCEPSS rescore
  38. 2026-06-10 13:20 UTCEPSS rescore
  39. 2026-06-08 14:15 UTCEPSS rescore
  40. 2026-06-08 14:15 UTCEPSS rescore
  41. 2026-06-07 15:23 UTCEPSS rescore
  42. 2026-06-07 15:23 UTCEPSS rescore
  43. 2026-06-06 13:46 UTCEPSS rescore
  44. 2026-06-06 13:46 UTCEPSS rescore
  45. 2026-06-06 13:46 UTCEPSS rescore
  46. 2026-06-05 22:45 UTCEPSS rescore
  47. 2026-06-05 22:45 UTCEPSS rescore
  48. 2026-06-05 06:09 UTCEPSS rescore
  49. 2026-06-05 06:09 UTCEPSS rescore
  50. 2026-06-05 06:08 UTCEPSS rescore
  51. 2026-06-02 20:11 UTCEPSS rescore
  52. 2026-06-02 20:11 UTCEPSS rescore
  53. 2026-06-01 13:50 UTCEPSS rescore
  54. 2026-06-01 13:50 UTCEPSS rescore
  55. 2026-05-31 22:29 UTCEPSS rescore
  56. 2026-05-31 22:29 UTCEPSS rescore
  57. 2026-05-31 00:15 UTCEPSS rescore
  58. 2026-05-31 00:15 UTCEPSS rescore
  59. 2026-05-29 13:42 UTCEPSS rescore
  60. 2026-05-26 14:34 UTCEG score recompute
  61. 2026-05-26 14:33 UTCGHSA enrichment
  62. 2026-05-26 07:17 UTCEPSS rescore
  63. 2026-05-26 07:17 UTCEPSS rescore
  64. 2026-05-25 07:07 UTCOSV refresh

Publicly available exploits

(1 reference)

Working exploit code is in the public domain (1 Metasploit module). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • Metasploitexploit/multi/http/moodle_spelling_path_rce✓ verified
    First seen Jun 22, 2021

    Moodle SpellChecker Path Authenticated Remote Command Execution

    Open source ↗

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2021-21809?
CVE-2021-21809 is a critical vulnerability published on June 23, 2021. A command execution vulnerability exists in the default legacy spellchecker plugin in Moodle 3.10. A specially crafted series of HTTP requests can lead to command execution. An attacker must have administrator privileges to exploit this vulnerabilities.
When was CVE-2021-21809 disclosed?
CVE-2021-21809 was first published in the National Vulnerability Database on June 23, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-21809 actively exploited?
CVE-2021-21809 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 97.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-21809?
CVE-2021-21809 has a CVSS v3 base score of 9.1 (NVD).
How do I remediate CVE-2021-21809?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-21809, 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-2021-21809

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