CVE-2021-20181

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2022-05-24. NVD baseline CVSS 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.5Exploit: None knownExposed: 0

A fix is available — apply it.

A race condition flaw was found in the 9pfs server implementation of QEMU up to and including 5.2.0. This flaw allows a malicious 9p client to cause a use-after-free error, potentially escalating their privileges on the system. The highest threat from this vulnerability is to confidentiality, integrity as well as system availability.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
38(Track)
EG Risk 38/100SSVC: 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
Severity75% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
25%
KEV
Not listed

Published

May 13, 2021

Last Modified

November 21, 2024

References (10)

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuqemu-utils (1:2.5+dfsg-5ubuntu10.49) @ xenial2026-05-26ubuntu

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

(6 across 6 ecosystems)
Debian:10(1)
PackageVulnerable rangeFixed inDependents
qemu1:3.1+dfsg-8 ... 1:3.1+dfsg-8~deb10u1 (9 versions)1:3.1+dfsg-8+deb10u9—
Debian:11(1)
PackageVulnerable rangeFixed inDependents
qemu—1:5.2+dfsg-4—
Debian:12(1)
PackageVulnerable rangeFixed inDependents
qemu—1:5.2+dfsg-4—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
qemu—1:5.2+dfsg-4—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
qemu—1:5.2+dfsg-4—
Debian:9(1)
PackageVulnerable rangeFixed inDependents
qemu1:2.8+dfsg-6 ... 1:2.8+dfsg-6+deb9u9 (13 versions)1:2.8+dfsg-6+deb9u13—

Weakness Classification(3)

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

All Vendor Advisories

(2)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 7× in last 7d / 29× 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.

Showing the most recent 100 of 157 total refreshes for this CVE.

  1. 2026-09-18 19:23 UTCEPSS rescore
  2. 2026-09-17 19:23 UTCEPSS rescore
  3. 2026-09-16 14:05 UTCEPSS rescore
  4. 2026-09-16 14:04 UTCEPSS rescore
  5. 2026-09-15 03:06 UTCEPSS rescore
  6. 2026-09-13 16:43 UTCEPSS rescore
  7. 2026-09-12 14:57 UTCEPSS rescore
  8. 2026-09-11 09:33 UTCEPSS rescore
  9. 2026-09-10 09:29 UTCEPSS rescore
  10. 2026-09-08 21:56 UTCEPSS rescore
  11. 2026-09-07 15:58 UTCEPSS rescore
  12. 2026-09-06 17:01 UTCOSV refresh
  13. 2026-09-06 13:44 UTCEPSS rescore
  14. 2026-09-06 13:44 UTCEPSS rescore
  15. 2026-09-05 15:25 UTCEPSS rescore
  16. 2026-09-04 13:57 UTCEPSS rescore
  17. 2026-09-04 05:03 UTCEPSS rescore
  18. 2026-09-02 14:08 UTCEPSS rescore
  19. 2026-09-01 13:50 UTCEPSS rescore
  20. 2026-09-01 03:32 UTCEPSS rescore
  21. 2026-08-30 19:14 UTCEPSS rescore
  22. 2026-08-30 01:19 UTCEPSS rescore
  23. 2026-08-28 21:37 UTCEPSS rescore
  24. 2026-08-27 14:22 UTCEPSS rescore
  25. 2026-08-26 14:42 UTCEPSS rescore
Show 75 more
  1. 2026-08-25 13:45 UTCEPSS rescore
  2. 2026-08-23 00:16 UTCEPSS rescore
  3. 2026-08-21 23:46 UTCEPSS rescore
  4. 2026-08-20 22:52 UTCEPSS rescore
  5. 2026-08-20 03:04 UTCOSV refresh
  6. 2026-08-19 17:01 UTCEPSS rescore
  7. 2026-08-18 13:45 UTCEPSS rescore
  8. 2026-08-17 13:43 UTCEPSS rescore
  9. 2026-08-16 14:52 UTCEPSS rescore
  10. 2026-08-16 02:11 UTCEPSS rescore
  11. 2026-08-15 01:27 UTCEPSS rescore
  12. 2026-08-13 21:57 UTCEPSS rescore
  13. 2026-08-12 13:47 UTCEPSS rescore
  14. 2026-08-11 13:38 UTCEPSS rescore
  15. 2026-08-09 13:43 UTCEPSS rescore
  16. 2026-08-07 16:23 UTCEPSS rescore
  17. 2026-08-06 13:43 UTCEPSS rescore
  18. 2026-08-05 19:14 UTCEPSS rescore
  19. 2026-08-04 22:10 UTCOSV refresh
  20. 2026-08-04 15:06 UTCEPSS rescore
  21. 2026-08-04 10:34 UTCEPSS rescore
  22. 2026-08-03 10:32 UTCEPSS rescore
  23. 2026-08-02 02:24 UTCEPSS rescore
  24. 2026-08-01 04:12 UTCEPSS rescore
  25. 2026-07-30 16:25 UTCEPSS rescore
  26. 2026-07-30 01:27 UTCEPSS rescore
  27. 2026-07-30 01:27 UTCEPSS rescore
  28. 2026-07-26 14:52 UTCEPSS rescore
  29. 2026-07-25 14:15 UTCEPSS rescore
  30. 2026-07-24 14:15 UTCEPSS rescore
  31. 2026-07-23 14:15 UTCEPSS rescore
  32. 2026-07-23 01:56 UTCEG score recompute
  33. 2026-07-22 22:43 UTCEG score recompute
  34. 2026-07-22 14:05 UTCEPSS rescore
  35. 2026-07-21 15:22 UTCEPSS rescore
  36. 2026-07-21 15:22 UTCEPSS rescore
  37. 2026-07-20 17:04 UTCEPSS rescore
  38. 2026-07-19 02:26 UTCEPSS rescore
  39. 2026-07-18 20:29 UTCOSV refresh
  40. 2026-07-18 10:02 UTCEPSS rescore
  41. 2026-07-16 17:00 UTCEPSS rescore
  42. 2026-07-15 16:55 UTCEPSS rescore
  43. 2026-07-15 16:55 UTCEPSS rescore
  44. 2026-07-15 01:57 UTCEPSS rescore
  45. 2026-07-13 22:27 UTCEPSS rescore
  46. 2026-07-13 22:27 UTCEPSS rescore
  47. 2026-07-13 06:10 UTCEPSS rescore
  48. 2026-07-13 06:10 UTCEPSS rescore
  49. 2026-07-12 05:44 UTCEPSS rescore
  50. 2026-07-12 05:44 UTCEPSS rescore
  51. 2026-07-11 08:25 UTCEPSS rescore
  52. 2026-07-09 19:07 UTCEPSS rescore
  53. 2026-07-08 15:12 UTCEPSS rescore
  54. 2026-07-07 13:43 UTCEPSS rescore
  55. 2026-07-06 16:25 UTCEPSS rescore
  56. 2026-07-06 02:21 UTCEPSS rescore
  57. 2026-07-06 02:21 UTCEPSS rescore
  58. 2026-07-05 02:28 UTCEPSS rescore
  59. 2026-07-05 02:28 UTCEPSS rescore
  60. 2026-07-04 06:29 UTCEPSS rescore
  61. 2026-07-04 06:29 UTCEPSS rescore
  62. 2026-07-02 16:57 UTCEPSS rescore
  63. 2026-07-01 15:03 UTCEPSS rescore
  64. 2026-07-01 03:48 UTCOSV refresh
  65. 2026-06-30 23:20 UTCEPSS rescore
  66. 2026-06-30 23:20 UTCEPSS rescore
  67. 2026-06-29 14:04 UTCEPSS rescore
  68. 2026-06-29 14:04 UTCEPSS rescore
  69. 2026-06-28 14:05 UTCEPSS rescore
  70. 2026-06-28 04:54 UTCEPSS rescore
  71. 2026-06-28 04:54 UTCEPSS rescore
  72. 2026-06-27 03:06 UTCEPSS rescore
  73. 2026-06-27 03:06 UTCEPSS rescore
  74. 2026-06-25 13:48 UTCEPSS rescore
  75. 2026-06-25 13:48 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2021-20181?
CVE-2021-20181 is a high vulnerability published on May 13, 2021. A race condition flaw was found in the 9pfs server implementation of QEMU up to and including 5.2.0. This flaw allows a malicious 9p client to cause a use-after-free error, potentially escalating their privileges on the system. The highest threat from this vulnerability is to confidentiality,…
When was CVE-2021-20181 disclosed?
CVE-2021-20181 was first published in the National Vulnerability Database on May 13, 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-2021-20181 actively exploited?
CVE-2021-20181 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 74.9% of all scored CVEs.
What is the CVSS score of CVE-2021-20181?
CVE-2021-20181 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2021-20181?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-20181, 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

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