Vulnerability · Published Jan 21, 2026 · Assigned by GitHub_M
CVE-2025-69209ArduinoCore-avr has Stack-Based Buffer Overflow in WString Float/Double Constructors
Medium 6.9
In plain English
A medium-severity buffer overflow in ArduinoCore-avr from arduino. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 7% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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/)
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | arduino-core-avr | 1.8.7+dfsg-1~deb12u1 | DEBIAN-CVE-2025-69209 |
| Debian:13 | arduino-core-avr | 1.8.7+dfsg-1~deb13u1 | DEBIAN-CVE-2025-69209 |
| Debian:14 | arduino-core-avr | 1.8.7+dfsg-1 | DEBIAN-CVE-2025-69209 |
| Ubuntu:22.04:LTS | arduino-core-avr | no fix listed | UBUNTU-CVE-2025-69209 |
| Ubuntu:24.04:LTS | arduino-core-avr | no fix listed | UBUNTU-CVE-2025-69209 |
| Ubuntu:25.10 | arduino-core-avr | no fix listed | UBUNTU-CVE-2025-69209 |
| Ubuntu:26.04:LTS | arduino-core-avr | no fix listed | UBUNTU-CVE-2025-69209 |
| Ubuntu:26.10 | arduino-core-avr | no fix listed | UBUNTU-CVE-2025-69209 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| arduino | ArduinoCore-avr | < 1.8.7 |
Weakness: CWE-120 · Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
References
- https://github.com/arduino/ArduinoCore-avr/security/advisories/GHSA-pvx3-fm7w-6hjm x_refsource_CONFIRM
- https://github.com/arduino/ArduinoCore-avr/pull/613 x_refsource_MISC
- https://github.com/arduino/ArduinoCore-avr/commit/82a8ad2fb33911d8927c7af22e0472b94325d1a7 x_refsource_MISC
- https://github.com/arduino/ArduinoCore-avr/releases/tag/1.8.7 x_refsource_MISC
- https://support.arduino.cc/hc/en-us/articles/24985906702748-ASEC-26-001-ArduinoCore-AVR-v1-8-7-Resolves-Stack-Based-Buffer-Overflow-Vulnerability x_refsource_MISC