CVE-2026-23833Network attack vector

Device crash via protobuf length integer overflow

Published Jan 19, 2026 · Updated Jan 19, 2026

Integer overflow in ESPHome's API protobuf decoder in versions 2025.9.0 through 2025.12.6 allows remote attackers to crash devices. The decoder in components/api/proto.cpp adds an attacker-controlled field_length to ptr, allowing pointer wraparound to bypass its end-of-buffer check and trigger an invalid memory read. Plaintext API access on TCP port 6053 requires no authentication; Noise-encrypted access requires the device key, and the bounded consequence is a device crash and reboot.

CVSS severity7.5
High
EPSS probability0.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer overflow in ESPHome's API protobuf decoder in versions 2025.9.0 through 2025.12.6 allows remote attackers to crash devices. The decoder in components/api/proto.cpp adds an attacker-controlled field_length to ptr, allowing pointer wraparound to bypass its end-of-buffer check and trigger an invalid memory read. Plaintext API access on TCP port 6053 requires no authentication; Noise-encrypted access requires the device key, and the bounded consequence is a device crash and reboot.

The record

CVE
CVE-2026-23833
Published
Jan 19, 2026
Updated
Jan 19, 2026
Vendor
ESPHome
Product
ESPHome
Classifications
CWE-190, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 19, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 2025.9.0, < 2025.12.7

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ESPHome · ESPHomeversion=>= 2025.9.0, < 2025.12.7

Published CVSS scores

1.7GitHub, Inc.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
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-190Integer Overflow or Wraparound
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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