ArduinoCore-avr has Stack-Based Buffer Overflow in WString Float/Double Constructors

{
  "id": "7baa1a95e299431cd93ce34edb42c4659fabccd91baba3112b632a9d85202eea",
  "url": "https://osv.dev/vulnerability/CVE-2025-69209",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ArduinoCore-avr has Stack-Based Buffer Overflow in WString Float/Double Constructors",
    "summary": "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/)",
    "evidence": "osv:CVE-2025-69209",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2025-69209",
      "aliases": [
        "CVE-2025-69209",
        "GHSA-pvx3-fm7w-6hjm"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "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"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/arduino/arduinocore-avr",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "d5d1355b95fd57bbcd30b86db5dc0003440eee8d"
                },
                {
                  "fixed": "82a8ad2fb33911d8927c7af22e0472b94325d1a7"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "1.8.7"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "82a8ad2fb33911d8927c7af22e0472b94325d1a7"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "d5d1355b95fd57bbcd30b86db5dc0003440eee8d"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "1.8.7"
                  }
                ]
              }
            }
          ],
          "versions": [
            "1.8.6",
            "1.8.5",
            "1.8.4",
            "1.8.3",
            "1.8.2",
            "1.8.1",
            "1.6.23",
            "1.6.22"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-69209.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:49.835734921Z",
      "provider": "osv",
      "references": [
        "https://github.com/arduino/ArduinoCore-avr/releases/tag/1.8.7",
        "https://support.arduino.cc/hc/en-us/articles/24985906702748-ASEC-26-001-ArduinoCore-AVR-v1-8-7-Resolves-Stack-Based-Buffer-Overflow-Vulnerability",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/69xxx/CVE-2025-69209.json",
        "https://github.com/arduino/ArduinoCore-avr/security/advisories/GHSA-pvx3-fm7w-6hjm",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-69209",
        "https://github.com/arduino/ArduinoCore-avr/commit/82a8ad2fb33911d8927c7af22e0472b94325d1a7",
        "https://github.com/arduino/ArduinoCore-avr/pull/613"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-120"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/69xxx/CVE-2025-69209.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-69209",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 518387,
  "published_at": "2026-01-21T20:00:41.026+00:00"
}