How severe is CVE-2026-23833?

CVE-2026-23833 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-23833 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (19th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-23833?

CVE-2026-23833 affects Esphome. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-23833?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-23833 have an EU (EUVD) identifier?

Yes. CVE-2026-23833 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-3306.

When was CVE-2026-23833 published?

CVE-2026-23833 was published on 2026-01-19 and last updated on 2026-06-17.

CVE-2026-23833

CVE-2026-23833 is a high-severity vulnerability in Esphome with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-190.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v4: 1.7
EPSS exploit prediction: 0% (19th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-3306
Weakness: CWE-190
Affected product: Esphome
Published: 2026-01-19
Last modified: 2026-06-17

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 > 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.

Frequently asked questions

What is CVE-2026-23833?: 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 > 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.
How severe is CVE-2026-23833?: CVE-2026-23833 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-23833 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (19th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-23833?: CVE-2026-23833 affects Esphome. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-23833?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-23833 have an EU (EUVD) identifier?: Yes. CVE-2026-23833 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-3306.
When was CVE-2026-23833 published?: CVE-2026-23833 was published on 2026-01-19 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:esphome:esphome:*:*:*:*:*:*:*:*

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