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CVE-2021-42553

32
FAUCET Score

CVE-2021-42553 is a critical buffer overflow vulnerability affecting STMicroelectronics' stm32_mw_usb_host library in versions prior to 3.5.1, commonly integrated into STM32 MCUs with RTOS like FreeRTOS. This flaw allows unauthenticated remote attackers to execute arbitrary code by crafting a descriptor with an excessive number of endpoints. With a CVSS score of 9.8 (CRITICAL), it presents a high risk for complete compromise of confidentiality, integrity, and availability. While there is no evidence of active exploitation or public exploit code, the vulnerability has garnered significant community discussion, indicating awareness among security researchers.

Impacted Technologies

VendorProductVersion(s)CPE
Range not provided by sourceCPE matchmatch criteria
cpe:2.3:a:st:stm32_mw_usb_host:-:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.8MEDIUM

CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
PHYSICAL
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
0.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.96%
Probability of exploitation in next 30 days
EPSS Percentile
57.8%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0096 is in the 43rd percentile among its peer group of 36,862 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

github_advisorypatch availablevia nvd_reference
View patch

References

github.com / STMicroelectronics/stm32_mw_usb_host
github.com / STMicroelectronics/stm32_mw_usb_host/pull/4
PatchThird Party Advisory