CVE-2021-3492

HIGHNVD 8.88.8—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.8 under NVD CVSS v3. EPSS exploit probability: 1.5%, top 28% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Elevated
8.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 2%CVSS: 8.8Exploit: NoneExposed: 0

A fix is available — apply it.

Shiftfs, an out-of-tree stacking file system included in Ubuntu Linux kernels, did not properly handle faults occurring during copy_from_user() correctly. These could lead to either a double-free situation or memory not being freed at all. An attacker could use this to cause a denial of service (kernel memory exhaustion) or gain privileges via executing arbitrary code. AKA ZDI-CAN-13562.

CVSS v3
8.8
EG Score
8.8(medium)
EG Risk
60(Track)
EG Risk 60/100SSVC: 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
Severity88% × 45%
Exploitation40% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
72.4%
KEV
Not listed

Published

April 17, 2021

Last Modified

November 21, 2024

References (12)

Patch Availability(3)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulinux-image-oem-20.04 (5.6.0.1054.50) @ focal2026-05-26ubuntu
ubuntulinux-image-virtual-hwe-20.04-edge (5.8.0.50.55) @ groovy2026-05-26ubuntu
ubuntulowlatency-5.4 (5.4.0-26) @ bionic2026-05-26ubuntu

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.

Weakness Classification(2)

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

All Vendor Advisories

(3)

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 12× in last 7d / 48× 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 02:01 UTCEG score recompute
  2. 2026-07-22 22:48 UTCEG score recompute
  3. 2026-07-22 14:06 UTCEPSS rescore
  4. 2026-07-21 15:22 UTCEPSS rescore
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  6. 2026-07-20 17:05 UTCEPSS rescore
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  18. 2026-07-13 06:11 UTCEPSS rescore
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  20. 2026-07-12 05:44 UTCEPSS rescore
  21. 2026-07-11 08:25 UTCEPSS rescore
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  23. 2026-07-09 19:07 UTCEPSS rescore
  24. 2026-07-08 15:12 UTCEPSS rescore
  25. 2026-07-07 13:43 UTCEPSS rescore
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  1. 2026-07-06 16:25 UTCEPSS rescore
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  3. 2026-07-06 02:21 UTCEPSS rescore
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  5. 2026-07-05 02:28 UTCEPSS rescore
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  7. 2026-07-04 06:29 UTCEPSS rescore
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  9. 2026-07-02 16:57 UTCEPSS rescore
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  11. 2026-06-30 23:20 UTCEPSS rescore
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  13. 2026-06-28 14:05 UTCEPSS rescore
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  16. 2026-06-27 03:06 UTCEPSS rescore
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  18. 2026-06-25 13:48 UTCEPSS rescore
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  20. 2026-06-24 14:03 UTCEPSS rescore
  21. 2026-06-24 14:03 UTCEPSS rescore
  22. 2026-06-23 21:31 UTCEPSS rescore
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  24. 2026-06-22 14:24 UTCEPSS rescore
  25. 2026-06-21 14:55 UTCEPSS rescore
  26. 2026-06-21 01:58 UTCEPSS rescore
  27. 2026-06-21 01:58 UTCEPSS rescore
  28. 2026-06-19 19:24 UTCEPSS rescore
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  30. 2026-06-18 17:51 UTCEPSS rescore
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  32. 2026-06-17 17:51 UTCEPSS rescore
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  35. 2026-06-16 17:51 UTCEPSS rescore
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  37. 2026-06-15 17:46 UTCEPSS rescore
  38. 2026-06-14 23:15 UTCEPSS rescore
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  40. 2026-06-13 22:58 UTCEPSS rescore
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  42. 2026-06-12 23:10 UTCEPSS rescore
  43. 2026-06-11 13:58 UTCEPSS rescore
  44. 2026-06-11 13:58 UTCEPSS rescore
  45. 2026-06-10 22:16 UTCEPSS rescore
  46. 2026-06-10 22:16 UTCEPSS rescore
  47. 2026-06-10 13:20 UTCEPSS rescore
  48. 2026-06-08 14:15 UTCEPSS rescore
  49. 2026-06-08 14:15 UTCEPSS rescore
  50. 2026-06-06 13:46 UTCEPSS rescore
  51. 2026-06-06 13:46 UTCEPSS rescore
  52. 2026-06-05 22:45 UTCEPSS rescore
  53. 2026-06-04 13:10 UTCEPSS rescore
  54. 2026-06-04 13:10 UTCEPSS rescore
  55. 2026-06-02 20:11 UTCEPSS rescore
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  57. 2026-06-01 13:50 UTCEPSS rescore
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  59. 2026-05-31 00:15 UTCEPSS rescore
  60. 2026-05-31 00:15 UTCEPSS rescore
  61. 2026-05-29 13:42 UTCEPSS rescore
  62. 2026-05-28 13:43 UTCEPSS rescore
  63. 2026-05-28 13:43 UTCEPSS rescore
  64. 2026-05-27 13:39 UTCEPSS rescore
  65. 2026-05-27 13:39 UTCEPSS rescore
  66. 2026-05-26 18:11 UTCEG score recompute
  67. 2026-05-26 18:11 UTCVendor advisory
  68. 2026-05-26 18:10 UTCGHSA enrichment
  69. 2026-05-26 13:42 UTCEPSS rescore
  70. 2026-05-26 13:42 UTCEPSS rescore

Publicly available exploits

(1 reference)

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

  • GitHub PoCsynacktiv/CVE-2021-3492
    First seen Jun 28, 2021

    PoC for CVE-2021-3492 used at Pwn2Own 2021

    Open source ↗

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2021-3492?
CVE-2021-3492 is a high vulnerability published on April 17, 2021. Shiftfs, an out-of-tree stacking file system included in Ubuntu Linux kernels, did not properly handle faults occurring during copyfromuser() correctly. These could lead to either a double-free situation or memory not being freed at all. An attacker could use this to cause a denial of service…
When was CVE-2021-3492 disclosed?
CVE-2021-3492 was first published in the National Vulnerability Database on April 17, 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-2021-3492 actively exploited?
CVE-2021-3492 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 72.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-3492?
CVE-2021-3492 has a CVSS v3 base score of 8.8 (NVD).
How do I remediate CVE-2021-3492?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-3492, 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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