No exploitation reportedFix available

CVE-2021-42553

Q: Is CVE-2021-42553 actively exploited?

Active exploitation of CVE-2021-42553 has not been confirmed. Its EPSS score was 1.3% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2021-42553?

CVE-2021-42553 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

No exploitation reported by the sources we read.

Published2022-10-21
Fixed in3.5.1
WeaknessCWE-120

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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.

Timeline

dates in UTC

2022-10-2110:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-42553?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-42553?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

St stm32 mw usb host

Branch	Affected	Fixed in	Source
3.5	< 3.5.1	3.5.1	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update St stm32 mw usb host to 3.5.1

Advisories and patches

github.comPatch

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

CISA-ADPSSVC decisionnone2025-05-07
OpenCVESSVC decisionnone—
CNACVSS 3.16.8read 2026-10-23
NVDCVSS 3.19.8read 2026-10-23
CISA-ADPweakness (CWE)CWE-1202025-05-07
NVDweakness (CWE)CWE-120read 2026-10-23
FIRST EPSSEPSS score1.3 %2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published: 2022-10-21
Last Modified: 2026-10-08
NVD status: Analyzed

Frequently asked questions

What is CVE-2021-42553?

Is CVE-2021-42553 actively exploited?

Active exploitation of CVE-2021-42553 has not been confirmed. Its EPSS score was 1.3% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-42553?

CVE-2021-42553 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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