CVE-2021-47566

HIGHNVD 7.87.8—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.8 under NVD CVSS v3. EPSS exploit probability: 0.2%, top 86% 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
7.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.8Exploit: NoneExposed: 0

A fix is available — apply it.

In the Linux kernel, the following vulnerability has been resolved:

proc/vmcore: fix clearing user buffer by properly using clear_user()

To clear a user buffer we cannot simply use memset, we have to use clear_user(). With a virtio-mem device that registers a vmcore_cb and has some logically unplugged memory inside an added Linux memory block, I can easily trigger a BUG by copying the vmcore via "cp":

systemd[1]: Starting Kdump Vmcore Save Service... kdump[420]: Kdump is using the default log level(3). kdump[453]: saving to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/ kdump[458]: saving vmcore-dmesg.txt to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/ kdump[465]: saving vmcore-dmesg.txt complete kdump[467]: saving vmcore BUG: unable to handle page fault for address: 00007f2374e01000 #PF: supervisor write access in kernel mode #PF: error_code(0x0003) - permissions violation PGD 7a523067 P4D 7a523067 PUD 7a528067 PMD 7a525067 PTE 800000007048f867 Oops: 0003 [#1] PREEMPT SMP NOPTI CPU: 0 PID: 468 Comm: cp Not tainted 5.15.0+ #6 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-27-g64f37cc530f1-prebuilt.qemu.org 04/01/2014 RIP: 0010:read_from_oldmem.part.0.cold+0x1d/0x86 Code: ff ff ff e8 05 ff fe ff e9 b9 e9 7f ff 48 89 de 48 c7 c7 38 3b 60 82 e8 f1 fe fe ff 83 fd 08 72 3c 49 8d 7d 08 4c 89 e9 89 e8 <49> c7 45 00 00 00 00 00 49 c7 44 05 f8 00 00 00 00 48 83 e7 f81 RSP: 0018:ffffc9000073be08 EFLAGS: 00010212 RAX: 0000000000001000 RBX: 00000000002fd000 RCX: 00007f2374e01000 RDX: 0000000000000001 RSI: 00000000ffffdfff RDI: 00007f2374e01008 RBP: 0000000000001000 R08: 0000000000000000 R09: ffffc9000073bc50 R10: ffffc9000073bc48 R11: ffffffff829461a8 R12: 000000000000f000 R13: 00007f2374e01000 R14: 0000000000000000 R15: ffff88807bd421e8 FS: 00007f2374e12140(0000) GS:ffff88807f000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f2374e01000 CR3: 000000007a4aa000 CR4: 0000000000350eb0 Call Trace: read_vmcore+0x236/0x2c0 proc_reg_read+0x55/0xa0 vfs_read+0x95/0x190 ksys_read+0x4f/0xc0 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae

Some x86-64 CPUs have a CPU feature called "Supervisor Mode Access Prevention (SMAP)", which is used to detect wrong access from the kernel to user buffers like this: SMAP triggers a permissions violation on wrong access. In the x86-64 variant of clear_user(), SMAP is properly handled via clac()+stac().

To fix, properly use clear_user() when we're dealing with a user buffer.

CVSS v3
7.8
EG Score
7.8(medium)
EG Risk
35(Track)
EG Risk 35/100SSVC: 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
Severity78% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
13.8%
KEV
Not listed

Published

May 24, 2024

Last Modified

September 18, 2025

References (16)

Vendor Advisories for CVE-2021-47566(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(2)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatkernel-0:4.18.0-477.74.1.el8_82024-09-24redhat
redhatkernel-0:4.18.0-372.118.1.el8_62024-08-13redhat

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(1)

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

Additional Vendor Advisories

(1)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 12× in last 7d / 50× 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 103 total refreshes for this CVE.

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

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2021-47566?
CVE-2021-47566 is a high vulnerability published on May 24, 2024. In the Linux kernel, the following vulnerability has been resolved: proc/vmcore: fix clearing user buffer by properly using clear_user() To clear a user buffer we cannot simply use memset, we have to use clearuser(). With a virtio-mem device that registers a vmcorecb and has some logically…
When was CVE-2021-47566 disclosed?
CVE-2021-47566 was first published in the National Vulnerability Database on May 24, 2024, with the most recent update on September 18, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-47566 actively exploited?
CVE-2021-47566 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 13.8% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-47566?
CVE-2021-47566 has a CVSS v3 base score of 7.8 (NVD).
How do I remediate CVE-2021-47566?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-47566, 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

Explore the affected products and dependency analysis for CVE-2021-47566

Explore →

Is Your Infrastructure Affected by CVE-2021-47566?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs