{"id":"CVE-2026-23833","aliases":["EUVD-2026-3306","GHSA-4h3h-63v6-88qx","PYSEC-2026-1326"],"status":"published","title":"ESPHome vulnerable to denial-of-service via out-of-bounds check bypass in the API component","description":"ESPHome is a system to control microcontrollers remotely through Home Automation systems. In versions 2025.9.0 through 2025.12.6, an integer overflow in the API component's protobuf decoder allows denial-of-service attacks when API encryption is not used. The bounds check `ptr + field_length \u003e end` in `components/api/proto.cpp` can overflow when a malicious client sends a large `field_length` value. This affects all ESPHome device platforms (ESP32, ESP8266, RP2040, LibreTiny). The overflow bypasses the out-of-bounds check, causing the device to read invalid memory and crash. When using the plaintext API protocol, this attack can be performed without authentication. When noise encryption is enabled, knowledge of the encryption key is required. Users should upgrade to ESPHome 2025.12.7 or later to receive a patch, enable API encryption with a unique key per device, and follow the Security Best Practices.","severity":{"version":"4.0","score":1.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U","level":"low","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00301,"percentile":0.23065,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-190"],"published":"2026-01-19T17:58:50Z","modified":"2026-10-28T10:51:14Z","fixes":[{"ecosystem":"PyPI","package":"esphome","fixed_in":["2025.12.7"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"esphome","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2025.9.0"},{"fixed":"2025.12.7"}]}]},{"source":"osv","ecosystem":"PyPI","package":"esphome","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2025.9.0"},{"fixed":"2025.12.7"}]}],"versions":["2025.10.0","2025.10.0b1","2025.10.0b2","2025.10.0b3","2025.10.0b4","2025.10.1","2025.10.2","2025.10.3","2025.10.4","2025.10.5","2025.11.0","2025.11.0b1","2025.11.0b2","2025.11.0b3","2025.11.0b4","2025.11.0b5","2025.11.1","2025.11.2","2025.11.3","2025.11.4","2025.11.5","2025.12.0","2025.12.0b1","2025.12.0b2","2025.12.0b3","2025.12.0b4","2025.12.0b5","2025.12.1","2025.12.2","2025.12.3","2025.12.4","2025.12.5","2025.12.6","2025.9.0","2025.9.1","2025.9.2","2025.9.3"]},{"source":"osv","ecosystem":"PyPI","package":"esphome","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2025.9.0"},{"fixed":"2025.12.7"}]}],"versions":["2025.10.0","2025.10.0b1","2025.10.0b2","2025.10.0b3","2025.10.0b4","2025.10.1","2025.10.2","2025.10.3","2025.10.4","2025.10.5","2025.11.0","2025.11.0b1","2025.11.0b2","2025.11.0b3","2025.11.0b4","2025.11.0b5","2025.11.1","2025.11.2","2025.11.3","2025.11.4","2025.11.5","2025.12.0","2025.12.0b1","2025.12.0b2","2025.12.0b3","2025.12.0b4","2025.12.0b5","2025.12.1","2025.12.2","2025.12.3","2025.12.4","2025.12.5","2025.12.6","2025.9.0","2025.9.1","2025.9.2","2025.9.3"]}],"products":[{"vendor":"esphome","product":"esphome"}],"references":[{"url":"https://github.com/esphome/esphome/security/advisories/GHSA-4h3h-63v6-88qx","tags":["x_refsource_CONFIRM","Mitigation","Patch","Vendor Advisory","advisory","web"]},{"url":"https://github.com/esphome/esphome/pull/13306","tags":["x_refsource_MISC","Issue Tracking","Patch","fix","web"]},{"url":"https://github.com/esphome/esphome/commit/69d7b6e9210390051318bd8e6410727689de08d6","tags":["x_refsource_MISC","Patch","fix","web"]},{"url":"https://esphome.io/guides/security_best_practices","tags":["x_refsource_MISC","Technical Description","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-23833","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-4h3h-63v6-88qx","tags":["advisory"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23833.json","tags":["advisory"]},{"url":"https://github.com/esphome/esphome","tags":["package"]},{"url":"https://pypi.org/project/esphome","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-23833","title":"ESPHome vulnerable to denial-of-service via out-of-bounds check bypass in the API component","description":"ESPHome is a system to control microcontrollers remotely through Home Automation systems. In versions 2025.9.0 through 2025.12.6, an integer overflow in the API component's protobuf decoder allows denial-of-service attacks when API encryption is not used. The bounds check `ptr + field_length \u003e end` in `components/api/proto.cpp` can overflow when a malicious client sends a large `field_length` value. This affects all ESPHome device platforms (ESP32, ESP8266, RP2040, LibreTiny). The overflow bypasses the out-of-bounds check, causing the device to read invalid memory and crash. When using the plaintext API protocol, this attack can be performed without authentication. When noise encryption is enabled, knowledge of the encryption key is required. Users should upgrade to ESPHome 2025.12.7 or later to receive a patch, enable API encryption with a unique key per device, and follow the Security Best Practices.","status":"published","published":"2026-01-19T17:58:50.499Z","modified":"2026-01-20T21:39:18.848Z","cvss":[{"version":"4.0","score":1.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U","level":"low","assessor":"cna"}],"cwes":["CWE-190"],"updated_at":"2026-11-02T13:42:15.603999Z"}],"euvd":[{"id":"EUVD-2026-3306","description":"ESPHome is a system to control microcontrollers remotely through Home Automation systems. In versions 2025.9.0 through 2025.12.6, an integer overflow in the API component's protobuf decoder allows denial-of-service attacks when API encryption is not used. The bounds check `ptr + field_length \u003e end` in `components/api/proto.cpp` can overflow when a malicious client sends a large `field_length` value. This affects all ESPHome device platforms (ESP32, ESP8266, RP2040, LibreTiny). The overflow bypasses the out-of-bounds check, causing the device to read invalid memory and crash. When using the plaintext API protocol, this attack can be performed without authentication. When noise encryption is enabled, knowledge of the encryption key is required. Users should upgrade to ESPHome 2025.12.7 or later to receive a patch, enable API encryption with a unique key per device, and follow the Security Best Practices.","status":"published","published":"2026-01-19T17:58:50Z","modified":"2026-01-20T21:39:18Z","cvss":[{"version":"4.0","score":1.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U","level":"low"}],"updated_at":"2026-11-02T19:48:49.964072Z"}],"ghsa":[{"id":"GHSA-4h3h-63v6-88qx","title":"ESPHome vulnerable to denial-of-service via out-of-bounds check bypass in the API component","description":"### Summary\nAn integer overflow in the API component's protobuf decoder allows denial-of-service attacks when API encryption is not used.\n\n### Details\nThe bounds check `ptr + field_length \u003e end` in `components/api/proto.cpp` can overflow when a malicious client sends a large `field_length` value. This affects all ESPHome device platforms (ESP32, ESP8266, RP2040, LibreTiny). The overflow bypasses the out-of-bounds check, causing the device to read invalid memory and crash.\n\nWhen using the plaintext API protocol, this attack can be performed without authentication. When noise encryption is enabled, knowledge of the encryption key is required.\n\n### Affected Versions\nESPHome 2025.9.0 through 2025.12.6\n\n### Mitigation\n- Upgrade to ESPHome 2025.12.7 or later (or 2026.1.0b3 or later)\n- [Enable API encryption](https://esphome.io/components/api.html#configuration-variables) with a unique key per device\n- Follow the [Security Best Practices](https://esphome.io/guides/security_best_practices/)\n\n### Severity\nLow - Users following [Security Best Practices](https://esphome.io/guides/security_best_practices/) with API encryption enabled are not affected without knowledge of the encryption key.\n\n### Impact\nDenial-of-service. An attacker with network access to port 6053 can crash and reboot the device.\n\n### Credits\nThanks to [@Mat931](https://github.com/Mat931) for responsibly reporting this vulnerability.","status":"published","published":"2026-01-21T01:02:49Z","modified":"2026-01-21T01:02:53Z","cvss":[{"version":"4.0","score":6.8,"vector":"CVSS:4.0/AV:A/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"medium"}],"cwes":["CWE-190"],"updated_at":"2026-11-02T14:39:18.564331Z"}],"nvd":[{"id":"CVE-2026-23833","description":"ESPHome is a system to control microcontrollers remotely through Home Automation systems. In versions 2025.9.0 through 2025.12.6, an integer overflow in the API component's protobuf decoder allows denial-of-service attacks when API encryption is not used. The bounds check `ptr + field_length \u003e end` in `components/api/proto.cpp` can overflow when a malicious client sends a large `field_length` value. This affects all ESPHome device platforms (ESP32, ESP8266, RP2040, LibreTiny). The overflow bypasses the out-of-bounds check, causing the device to read invalid memory and crash. When using the plaintext API protocol, this attack can be performed without authentication. When noise encryption is enabled, knowledge of the encryption key is required. Users should upgrade to ESPHome 2025.12.7 or later to receive a patch, enable API encryption with a unique key per device, and follow the Security Best Practices.","status":"published","published":"2026-01-19T18:16:06.007Z","modified":"2026-06-17T10:22:10.463Z","cvss":[{"version":"4.0","score":1.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"low","assessor":"secondary"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"primary"}],"cwes":["CWE-190"],"updated_at":"2026-11-02T14:12:04.066712Z"}],"osv":[{"id":"CVE-2026-23833","title":"ESPHome vulnerable to denial-of-service via out-of-bounds check bypass in the API component","description":"ESPHome is a system to control microcontrollers remotely through Home Automation systems. In versions 2025.9.0 through 2025.12.6, an integer overflow in the API component's protobuf decoder allows denial-of-service attacks when API encryption is not used. The bounds check `ptr + field_length \u003e end` in `components/api/proto.cpp` can overflow when a malicious client sends a large `field_length` value. This affects all ESPHome device platforms (ESP32, ESP8266, RP2040, LibreTiny). The overflow bypasses the out-of-bounds check, causing the device to read invalid memory and crash. When using the plaintext API protocol, this attack can be performed without authentication. When noise encryption is enabled, knowledge of the encryption key is required. Users should upgrade to ESPHome 2025.12.7 or later to receive a patch, enable API encryption with a unique key per device, and follow the Security Best Practices.","status":"published","published":"2026-01-19T17:58:50.499Z","modified":"2026-10-28T10:51:14.587345901Z","cvss":[{"version":"4.0","score":1.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U","level":"low"}],"cwes":["CWE-190"],"updated_at":"2026-11-02T15:44:59.079784Z"},{"id":"GHSA-4h3h-63v6-88qx","title":"ESPHome vulnerable to denial-of-service via out-of-bounds check bypass in the API component","description":"### Summary\nAn integer overflow in the API component's protobuf decoder allows denial-of-service attacks when API encryption is not used.\n\n### Details\nThe bounds check `ptr + field_length \u003e end` in `components/api/proto.cpp` can overflow when a malicious client sends a large `field_length` value. This affects all ESPHome device platforms (ESP32, ESP8266, RP2040, LibreTiny). The overflow bypasses the out-of-bounds check, causing the device to read invalid memory and crash.\n\nWhen using the plaintext API protocol, this attack can be performed without authentication. When noise encryption is enabled, knowledge of the encryption key is required.\n\n### Affected Versions\nESPHome 2025.9.0 through 2025.12.6\n\n### Mitigation\n- Upgrade to ESPHome 2025.12.7 or later (or 2026.1.0b3 or later)\n- [Enable API encryption](https://esphome.io/components/api.html#configuration-variables) with a unique key per device\n- Follow the [Security Best Practices](https://esphome.io/guides/security_best_practices/)\n\n### Severity\nLow - Users following [Security Best Practices](https://esphome.io/guides/security_best_practices/) with API encryption enabled are not affected without knowledge of the encryption key.\n\n### Impact\nDenial-of-service. An attacker with network access to port 6053 can crash and reboot the device.\n\n### Credits\nThanks to [@Mat931](https://github.com/Mat931) for responsibly reporting this vulnerability.","status":"published","published":"2026-01-21T01:02:49Z","modified":"2026-07-07T17:56:35.058004084Z","cvss":[{"version":"4.0","score":6.8,"vector":"CVSS:4.0/AV:A/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"medium"}],"cwes":["CWE-190"],"updated_at":"2026-11-02T15:46:37.148947Z"},{"id":"PYSEC-2026-1326","title":"ESPHome vulnerable to denial-of-service via out-of-bounds check bypass in the API component","description":"### Summary\nAn integer overflow in the API component's protobuf decoder allows denial-of-service attacks when API encryption is not used.\n\n### Details\nThe bounds check `ptr + field_length \u003e end` in `components/api/proto.cpp` can overflow when a malicious client sends a large `field_length` value. This affects all ESPHome device platforms (ESP32, ESP8266, RP2040, LibreTiny). The overflow bypasses the out-of-bounds check, causing the device to read invalid memory and crash.\n\nWhen using the plaintext API protocol, this attack can be performed without authentication. When noise encryption is enabled, knowledge of the encryption key is required.\n\n### Affected Versions\nESPHome 2025.9.0 through 2025.12.6\n\n### Mitigation\n- Upgrade to ESPHome 2025.12.7 or later (or 2026.1.0b3 or later)\n- [Enable API encryption](https://esphome.io/components/api.html#configuration-variables) with a unique key per device\n- Follow the [Security Best Practices](https://esphome.io/guides/security_best_practices/)\n\n### Severity\nLow - Users following [Security Best Practices](https://esphome.io/guides/security_best_practices/) with API encryption enabled are not affected without knowledge of the encryption key.\n\n### Impact\nDenial-of-service. An attacker with network access to port 6053 can crash and reboot the device.\n\n### Credits\nThanks to [@Mat931](https://github.com/Mat931) for responsibly reporting this vulnerability.","status":"published","published":"2026-07-07T16:03:19.321187Z","modified":"2026-07-07T17:46:44.629274708Z","cvss":[{"version":"4.0","score":6.8,"vector":"CVSS:4.0/AV:A/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"medium"}],"updated_at":"2026-11-02T15:52:54.622769Z"}]}}