CVE-2021-28689

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: 0.4%CVSS: 5.5Exploit: None knownExposed services: Not assessed

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

x86: Speculative vulnerabilities with bare (non-shim) 32-bit PV guests 32-bit x86 PV guest kernels run in ring 1. At the time when Xen was developed, this area of the i386 architecture was rarely used, which is why Xen was able to use it to implement paravirtualisation, Xen's novel approach to virtualization. In AMD64, Xen had to use a different implementation approach, so Xen does not use ring 1 to support 64-bit guests. With the focus now being on 64-bit systems, and the availability of explicit hardware support for virtualization, fixing speculation issues in ring 1 is not a priority for processor companies. Indirect Branch Restricted Speculation (IBRS) is an architectural x86 extension put together to combat speculative execution sidechannel attacks, including Spectre v2. It was retrofitted in microcode to existing CPUs. For more details on Spectre v2, see: http://xenbits.xen.org/xsa/advisory-254.html However, IBRS does not architecturally protect ring 0 from predictions learnt in ring 1. For more details, see: https://software.intel.com/security-software-guidance/deep-dives/deep-dive-indirect-branch-restricted-speculation Similar situations may exist with other mitigations for other kinds of speculative execution attacks. The situation is quite likely to be similar for speculative execution attacks which have yet to be discovered, disclosed, or mitigated.

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: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high, and watch the vendor's advisory for the fix.
EPSS PROB
0.4%
EPSS %ILE
27th
KEV
Not listed

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

No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high, and watch the vendor's advisory for the fix.

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

June 11, 2021

Last Modified

November 21, 2024

References (2)

Affected Packages

(4 across 4 ecosystems)
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
xen4.14.2+25-gb6a8c4f72d-2 ... 4.20.3+127-gc42374a105-1 (46 versions)
  • every version on: no fix on record
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
xen4.17.1+2-gb773c48e36-1 ... 4.20.3+127-gc42374a105-1 (25 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
xen4.20.0+68-g35cb38b222-1 ... 4.20.3+127-gc42374a105-1 (8 versions)
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
xen4.20.0+68-g35cb38b222-1, 4.20.2+37-g61ff35323e-1, 4.20.2+7-g1badcf5035-1, 4.20.2+7-g1badcf5035-2, 4.20.3+127-gc42374a105-1
  • every version on: no fix on record
—

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 33× 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 185 total refreshes for this CVE.

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

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Frequently asked(5)

What is CVE-2021-28689?
CVE-2021-28689 is a medium vulnerability published on June 11, 2021. x86: Speculative vulnerabilities with bare (non-shim) 32-bit PV guests 32-bit x86 PV guest kernels run in ring 1. At the time when Xen was developed, this area of the i386 architecture was rarely used, which is why Xen was able to use it to implement paravirtualisation, Xen's novel approach to…
When was CVE-2021-28689 disclosed?
CVE-2021-28689 was first published on June 11, 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-2021-28689 actively exploited?
CVE-2021-28689 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (27th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2021-28689?
CVE-2021-28689 has a CVSS v3 base score of 5.5 (NVD).
How do I remediate CVE-2021-28689?
No fix for CVE-2021-28689 is confirmed yet. Until one is published, restrict network exposure of the affected system or apply the vendor's mitigation — for example, keep it off the internet or limit it to trusted networks — and watch the vendor's advisory for the fix.

Dependency Blast Radius

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