CVE-2021-42553

CRITICALNVD 9.89.8
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to NVD's CVSS score.

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2022-10-21. NVD baseline CVSS 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, NVD CVSS v3
Trending — 4 sources updated this week
9.8EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1.3%CVSS: 9.8Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

A buffer overflow vulnerability in stm32_mw_usb_host of STMicroelectronics in versions before 3.5.1 allows an attacker to execute arbitrary code when the descriptor contains more endpoints than USBH_MAX_NUM_ENDPOINTS. The library is typically integrated when using a RTOS such as FreeRTOS on STM32 MCUs.

CVSS v3
9.8
EG Score
9.8CRITICALmedium confidence
EG Risk
45
EG Risk 45/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity98% × 45%
Impact severity (EG Severity): CVSS 9.8 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation1.3% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
1.3%
EPSS %ILE
69th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (9.8): severity, escalated by confirmed exploitation. This CVE's 9.8 is its impact severity (EG Severity), not escalated.

EG Severity
9.8 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
1.3% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-22). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

October 21, 2022

Last Modified

October 8, 2026

Advisory Details (2)

Auto-updated Oct 23, 2026
Patch available. Sources: github_pr.
GitHub pull request

Fix buffer overflow

Fix merged in STMicroelectronics/stm32_mw_usb_host PR #4 on 2023-03-29 — awaiting tagged release

https://github.com/STMicroelectronics/stm32_mw_usb_host/pull/4
Web page

GitHub - STMicroelectronics/stm32-mw-usb-host: Provides the USB Host library part of the STM32Cube MCU Component "middleware" for all STM32xx series. · GitHub

https://github.com/STMicroelectronics/stm32_mw_usb_host

Patch Availability(1)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntumicropython-doc (1.12-1ubuntu0.1~esm1) @ focal2026-10-22ubuntu

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.

All Vendor Advisories

(1)

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 25× in last 7d / 64× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 96 of 231 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 4 repeat rows among the latest 100 are merged into the row they repeat. The 135 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-22 23:14 UTCEG score recompute
  2. 2026-10-22 23:14 UTCVendor advisory
  3. 2026-10-22 23:14 UTCGHSA enrichmentGHSA-vwmv-9r25-j98p · GitHub severity CRITICAL · GitHub CVSS 9.8
  4. 2026-10-22 16:29 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  5. 2026-10-22 00:47 UTCEG score recompute
  6. 2026-10-22 00:47 UTCVendor advisory
  7. 2026-10-22 00:47 UTCGHSA enrichmentGHSA-vwmv-9r25-j98p · GitHub severity CRITICAL · GitHub CVSS 9.8
  8. 2026-10-21 16:28 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  9. 2026-10-21 02:09 UTCEG score recompute
  10. 2026-10-21 02:09 UTCVendor advisory
  11. 2026-10-21 02:09 UTCGHSA enrichmentGHSA-vwmv-9r25-j98p · GitHub severity CRITICAL · GitHub CVSS 9.8
  12. 2026-10-20 16:28 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  13. 2026-10-20 03:38 UTCEG score recompute
  14. 2026-10-20 03:38 UTCGHSA enrichmentGHSA-vwmv-9r25-j98p · GitHub severity CRITICAL · GitHub CVSS 9.8
  15. 2026-10-19 16:28 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  16. 2026-10-19 04:15 UTCEG score recompute
  17. 2026-10-19 04:15 UTCGHSA enrichmentGHSA-vwmv-9r25-j98p · GitHub severity CRITICAL · GitHub CVSS 9.8
  18. 2026-10-18 16:28 UTCEPSS rescoreEPSS 1.3% · 69th percentile
  19. 2026-10-18 05:46 UTCEG score recompute
  20. 2026-10-18 05:46 UTCGHSA enrichmentGHSA-vwmv-9r25-j98p · GitHub severity CRITICAL · GitHub CVSS 9.8
  21. 2026-10-17 16:29 UTCEPSS rescoreEPSS 1.1% · 64th percentile
  22. 2026-10-17 07:17 UTCEG score recompute
  23. 2026-10-17 07:17 UTCVendor advisory
  24. 2026-10-17 07:17 UTCGHSA enrichmentGHSA-vwmv-9r25-j98p · GitHub severity CRITICAL · GitHub CVSS 9.8
  25. 2026-10-16 16:34 UTCEPSS rescoreEPSS 1.1% · 64th percentile
Show 71 more
  1. 2026-10-16 08:48 UTCEG score recompute
  2. 2026-10-16 08:47 UTCGHSA enrichmentGHSA-vwmv-9r25-j98p · GitHub severity CRITICAL · GitHub CVSS 9.8
  3. 2026-10-15 16:28 UTCEPSS rescoreEPSS 1.1% · 64th percentile
  4. 2026-10-15 08:00 UTCEG score recompute
  5. 2026-10-15 07:59 UTCGHSA enrichmentGHSA-vwmv-9r25-j98p · GitHub severity CRITICAL · GitHub CVSS 9.8
  6. 2026-10-14 16:29 UTCEPSS rescoreEPSS 1.1% · 64th percentile
  7. 2026-10-14 03:59 UTCEG score recompute
  8. 2026-10-14 03:59 UTCVendor advisory
  9. 2026-10-14 03:59 UTCGHSA enrichmentGHSA-vwmv-9r25-j98p · GitHub severity CRITICAL · GitHub CVSS 9.8
  10. 2026-10-13 16:28 UTCEPSS rescoreEPSS 1.1% · 63rd percentile
  11. 2026-10-12 23:52 UTCVendor advisory
  12. 2026-10-12 23:52 UTCGHSA enrichmentGHSA-vwmv-9r25-j98p · GitHub severity CRITICAL · GitHub CVSS 9.8
  13. 2026-10-12 19:09 UTCEG score recompute
  14. 2026-10-12 16:30 UTCEPSS rescoreEPSS 1.1% · 63rd percentile
  15. 2026-10-11 23:34 UTCEG score recompute
  16. 2026-10-11 13:44 UTCEPSS rescoreEPSS 1.1% · 63rd percentile
  17. 2026-10-10 19:56 UTCEPSS rescoreEPSS 1.1% · 63rd percentile
  18. 2026-10-09 20:04 UTCEPSS rescoreEPSS 1.1% · 63rd percentile
  19. 2026-10-08 18:31 UTCEG score recompute
  20. 2026-10-08 18:31 UTCVendor advisory
  21. 2026-10-08 18:31 UTCGHSA enrichmentGHSA-vwmv-9r25-j98p · GitHub severity CRITICAL · GitHub CVSS 9.8
  22. 2026-10-08 18:24 UTCNVD updateCVSS v3 → 9.8 · severity → CRITICAL
  23. 2026-10-08 16:40 UTCEPSS rescoreEPSS 1.1% · 63rd percentile
  24. 2026-10-07 23:45 UTCEPSS rescoreEPSS 1.1% · 63rd percentile
  25. 2026-10-06 15:14 UTCEPSS rescoreEPSS 1.1% · 63rd percentile
  26. 2026-10-05 17:40 UTCEPSS rescoreEPSS 1.1% · 63rd percentile
  27. 2026-10-04 23:19 UTCEPSS rescoreEPSS 1.1% · 63rd percentile
  28. 2026-10-03 14:22 UTCEPSS rescoreEPSS 1.1% · 63rd percentile
  29. 2026-10-02 16:23 UTCEPSS rescoreEPSS 1.1% · 63rd percentile
  30. 2026-10-01 19:46 UTCEPSS rescoreEPSS 1.1% · 63rd percentile
  31. 2026-09-30 15:42 UTCEG score recompute
  32. 2026-09-30 15:00 UTCEPSS rescoreEPSS 1.1% · 63rd percentile
  33. 2026-09-29 15:15 UTCEPSS rescoreEPSS 1.1% · 63rd percentile
  34. 2026-09-28 13:47 UTCEPSS rescoreEPSS 1.1% · 63rd percentile
  35. 2026-09-27 13:41 UTCEPSS rescoreEPSS 1.1% · 63rd percentile
  36. 2026-09-26 15:54 UTCEPSS rescoreEPSS 1.1% · 63rd percentile
  37. 2026-09-26 00:21 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  38. 2026-09-24 14:00 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  39. 2026-09-24 07:19 UTCOSV refresh
  40. 2026-09-23 13:44 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  41. 2026-09-22 14:44 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  42. 2026-09-21 20:28 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  43. 2026-09-20 20:13 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  44. 2026-09-19 15:38 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  45. 2026-09-18 19:23 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  46. 2026-09-17 19:23 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  47. 2026-09-16 14:05 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  48. 2026-09-15 03:06 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  49. 2026-09-12 14:57 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  50. 2026-09-11 14:49 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  51. 2026-09-11 09:33 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  52. 2026-09-08 21:56 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  53. 2026-09-07 15:58 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  54. 2026-09-06 13:45 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  55. 2026-09-05 15:25 UTCEPSS rescoreEPSS 1.1% · 61st percentile
  56. 2026-09-05 00:44 UTCOSV refresh
  57. 2026-09-04 13:57 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  58. 2026-09-04 05:03 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  59. 2026-09-02 14:09 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  60. 2026-09-01 13:50 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  61. 2026-09-01 03:33 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  62. 2026-08-30 19:14 UTCEPSS rescoreEPSS 1.1% · 62nd percentile
  63. 2026-08-30 01:19 UTCEPSS rescoreEPSS 1.1% · 61st percentile
  64. 2026-08-28 21:37 UTCEPSS rescoreEPSS 1.1% · 61st percentile
  65. 2026-08-27 14:22 UTCEPSS rescoreEPSS 1.1% · 61st percentile
  66. 2026-08-26 14:43 UTCEPSS rescoreEPSS 1.1% · 61st percentile
  67. 2026-08-25 13:46 UTCEPSS rescoreEPSS 1.1% · 61st percentile
  68. 2026-08-24 14:13 UTCEPSS rescoreEPSS 1.1% · 61st percentile
  69. 2026-08-23 00:16 UTCEPSS rescoreEPSS 1.1% · 61st percentile
  70. 2026-08-21 23:46 UTCEPSS rescoreEPSS 1.1% · 61st percentile
  71. 2026-08-20 22:52 UTCEPSS rescoreEPSS 1.0% · 60th percentile

Related CVEs(same vendor + same CWE)

Same vendor

2 shown

ubuntu:USN-7472-1

Frequently asked(5)

What is CVE-2021-42553?
CVE-2021-42553 is a critical-severity vulnerability; its CVE record was published on October 21, 2022. A buffer overflow vulnerability in stm32mwusbhost of STMicroelectronics in versions before 3.5.1 allows an attacker to execute arbitrary code when the descriptor contains more endpoints than USBHMAXNUMENDPOINTS. The library is typically integrated when using a RTOS such as FreeRTOS on STM32 MCUs.
When was the CVE record for CVE-2021-42553 published?
The CVE record for CVE-2021-42553 was published on October 21, 2022. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 8, 2026; the record at its source may have been updated since.
Is CVE-2021-42553 actively exploited?
CVE-2021-42553 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1.3% probability of exploitation in the next 30 days (69th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2021-42553?
CVE-2021-42553 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2021-42553?
A fix for CVE-2021-42553 is available: update to the fixed version the vendor names in its advisory.

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