CVE-2021-26933

MEDIUMNVD 5.55.5—
EchelonGraph scoreMEDIUM confidence

Score 5.5 from GitHub Security Advisory published 2022-05-24. NVD baseline CVSS 5.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
5.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 5.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

An issue was discovered in Xen 4.9 through 4.14.x. On Arm, a guest is allowed to control whether memory accesses are bypassing the cache. This means that Xen needs to ensure that all writes (such as the ones during scrubbing) have reached the memory before handing over the page to a guest. Unfortunately, the operation to clean the cache is happening before checking if the page was scrubbed. Therefore there is no guarantee when all the writes will reach the memory.

CVSS v3
5.5
EG Score
5.5MEDIUMmedium confidence
EG Risk
29
EG Risk 29/100CISA SSVC

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
Severity55% × 45%
Exploitation0% × 40%
Automatability30% × 15%
CISA SSVC: Track at low or medium mission impact; Track or Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.3%
EPSS %ILE
23rd
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track or Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (no KEV listing, exploit record or EPSS ≥ 50%) · Automatable unknown (not published for this CVE) · Technical impact partial (CVSS below 9.0). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

February 17, 2021

Last Modified

November 21, 2024

References (8)

Affected Packages

(19 across 19 ecosystems)
Alpine:v3.11(1)
PackageVulnerable rangeFix by version rangeDependents
xen—
  • 4.9.0 up to 4.13.2-r5: fixed in 4.13.2-r5
—
Alpine:v3.12(1)
PackageVulnerable rangeFix by version rangeDependents
xen—
  • 4.9.0 up to 4.13.2-r5: fixed in 4.13.2-r5
—
Alpine:v3.13(1)
PackageVulnerable rangeFix by version rangeDependents
xen—
  • 4.9.0 up to 4.14.1-r2: fixed in 4.14.1-r2
—
Alpine:v3.14(1)
PackageVulnerable rangeFix by version rangeDependents
xen—
  • 4.9.0 up to 4.14.1-r3: fixed in 4.14.1-r3
—
Alpine:v3.15(1)
PackageVulnerable rangeFix by version rangeDependents
xen—
  • 4.9.0 up to 4.14.1-r3: fixed in 4.14.1-r3
—
Alpine:v3.16(1)
PackageVulnerable rangeFix by version rangeDependents
xen—
  • 4.9.0 up to 4.14.1-r3: fixed in 4.14.1-r3
—
Alpine:v3.17(1)
PackageVulnerable rangeFix by version rangeDependents
xen—
  • 4.9.0 up to 4.14.1-r3: fixed in 4.14.1-r3
—
Alpine:v3.18(1)
PackageVulnerable rangeFix by version rangeDependents
xen—
  • 4.9.0 up to 4.14.1-r3: fixed in 4.14.1-r3
—
Alpine:v3.19(1)
PackageVulnerable rangeFix by version rangeDependents
xen—
  • 4.9.0 up to 4.14.1-r3: fixed in 4.14.1-r3
—
Alpine:v3.20(1)
PackageVulnerable rangeFix by version rangeDependents
xen—
  • 4.9.0 up to 4.14.1-r3: fixed in 4.14.1-r3
—
Alpine:v3.21(1)
PackageVulnerable rangeFix by version rangeDependents
xen—
  • 4.9.0 up to 4.14.1-r3: fixed in 4.14.1-r3
—
Alpine:v3.22(1)
PackageVulnerable rangeFix by version rangeDependents
xen—
  • 4.9.0 up to 4.14.1-r3: fixed in 4.14.1-r3
—
Alpine:v3.23(1)
PackageVulnerable rangeFix by version rangeDependents
xen—
  • 4.9.0 up to 4.14.1-r3: fixed in 4.14.1-r3
—
Alpine:v3.24(1)
PackageVulnerable rangeFix by version rangeDependents
xen—
  • 4.9.0 up to 4.14.1-r3: fixed in 4.14.1-r3
—
Debian:10(1)
PackageVulnerable rangeFix by version rangeDependents
xen4.11.1+92-g6c33308a8d-2 ... 4.11.4-1 (9 versions)
  • every version up to 4.11.4+99-g8bce4698f6-1: fixed in 4.11.4+99-g8bce4698f6-1
—
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
xen—
  • every version up to 4.14.1+11-gb0b734a8b3-1: fixed in 4.14.1+11-gb0b734a8b3-1
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
xen—
  • every version up to 4.14.1+11-gb0b734a8b3-1: fixed in 4.14.1+11-gb0b734a8b3-1
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
xen—
  • every version up to 4.14.1+11-gb0b734a8b3-1: fixed in 4.14.1+11-gb0b734a8b3-1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
xen—
  • every version up to 4.14.1+11-gb0b734a8b3-1: fixed in 4.14.1+11-gb0b734a8b3-1
—

Data Freshness Timeline

(refreshed 9× in last 7d / 32× 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 184 total refreshes for this CVE.

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

Related CVEs(same product)· as of October 5, 2026

Frequently asked(5)

What is CVE-2021-26933?
CVE-2021-26933 is a medium vulnerability published on February 17, 2021. An issue was discovered in Xen 4.9 through 4.14.x. On Arm, a guest is allowed to control whether memory accesses are bypassing the cache. This means that Xen needs to ensure that all writes (such as the ones during scrubbing) have reached the memory before handing over the page to a guest.…
When was CVE-2021-26933 disclosed?
CVE-2021-26933 was first published on February 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-2021-26933 actively exploited?
CVE-2021-26933 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (23rd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2021-26933?
CVE-2021-26933 has a CVSS v3 base score of 5.5 (NVD).
How do I remediate CVE-2021-26933?
A fix for CVE-2021-26933 is available: update to the fixed version the vendor names in its advisory.

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