# CVE-2025-69209: arduino-core-avr: ArduinoCore-avr contains the source code and configuration files of the Arduino AVR Boards platform

CVE-2025-69209 is fixed in arduino-core-avr on 1 platform, first by DEBIAN-CVE-2025-69209, released January 21, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2025-69209
- Priority: Routine
- CVSS: n/a
- EPSS: 0.0018
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jan 21, 2026

## Description

ArduinoCore-avr contains the source code and configuration files of the Arduino AVR Boards platform. A vulnerability in versions prior to 1.8.7 allows an attacker to trigger a stack-based buffer overflow when converting floating-point values to strings with high precision. By passing very large `decimalPlaces` values to the affected String constructors or concat methods, the `dtostrf` function writes beyond fixed-size stack buffers, causing memory corruption and denial of service. Under specific conditions, this could enable arbitrary code execution on AVR-based Arduino boards.  ### Patches  - The Fix is included starting from the `1.8.7` release available from the following link [ArduinoCore-avr v1.8.7](https://github.com/arduino/ArduinoCore-avr)  - The Fixing Commit is available at the following link [1a6a417f89c8901dad646efce74ae9d3ddebfd59](https://github.com/arduino/ArduinoCore-avr/pull/613/commits/1a6a417f89c8901dad646efce74ae9d3ddebfd59)  ### References  - [ASEC-26-001 ArduinoCore-avr vXXXX Resolves Buffer Overflow Vulnerability](https://support.arduino.cc/hc/en-us/articles/XXXXX)  ### Credits  - Maxime Rossi Bellom and Ramtine Tofighi Shirazi from SecMate (https://secmate.dev/)

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | arduino-core-avr Debian 12.15 (bookworm) | 1.8.7+dfsg-1~deb12u1 | [DEBIAN-CVE-2025-69209](https://patchblox.com/security/data/fix/linux/debian-cve-2025-69209.md) | Jan 21, 2026 |
| Linux | arduino-core-avr Debian 13.5 (trixie) | 1.8.7+dfsg-1~deb13u1 | [DEBIAN-CVE-2025-69209](https://patchblox.com/security/data/fix/linux/debian-cve-2025-69209.md) | Jan 21, 2026 |
| Linux | arduino-core-avr Debian 14 | 1.8.7+dfsg-1 | [DEBIAN-CVE-2025-69209](https://patchblox.com/security/data/fix/linux/debian-cve-2025-69209.md) | Jan 21, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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