How severe is CVE-2026-23833?

No CVSS score has been assigned to CVE-2026-23833 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-23833?

CVE-2026-23833 affects the following packages: esphome (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-23833?

Update esphome to 2025.12.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-23833 is resolved across your whole dependency graph.

How do I detect CVE-2026-23833 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for esphome, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-23833 if there is no patch (or I can't update yet)?

Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.

Is CVE-2026-23833 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-23833 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-23833?

CVE-2026-23833 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 23th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-23833?

CVE-2026-23833 is classified as CWE-190 (CWE-190). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-23833 published, and has it been updated?

CVE-2026-23833 was published on January 19, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

CVE-2026-23833 — esphome

Fix: esphome/esphome@69d7b6e

CVE-2026-23833 is a CWE-190 vulnerability in esphome. A fix is available for esphome — see the affected versions and patch details below.

ESPHome vulnerable to denial-of-service via out-of-bounds check bypass in the API component

Also known asGHSA-4h3h-63v6-88qxPYSEC-2026-1326

Published

Jan 19, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-23833.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs23th percentile — riskier than 23% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐍esphome

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Summary

An integer overflow in the API component's protobuf decoder allows denial-of-service attacks when API encryption is not used.

Details

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.

Affected Versions

ESPHome 2025.9.0 through 2025.12.6

Mitigation

Upgrade to ESPHome 2025.12.7 or later (or 2026.1.0b3 or later)
Enable API encryption with a unique key per device
Follow the Security Best Practices

Severity

Low - Users following Security Best Practices with API encryption enabled are not affected without knowledge of the encryption key.

Impact

Denial-of-service. An attacker with network access to port 6053 can crash and reboot the device.

Credits

Thanks to @Mat931 for responsibly reporting this vulnerability.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`esphome`	≥ 2025.9.0&&< 2025.12.7	2025.12.7`pip install --upgrade 'esphome==2025.12.7'`

Affected Products

1 product · 1 configurations

Application

esphomeesphome

≥ 2025.9.0 && < 2025.12.7

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for esphome, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update esphome to 2025.12.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-23833 is resolved across your whole dependency graph.
Workarounds
Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatLow

This vulnerability is rated Low for Red Hat. The flaw in ESPHome's API component, affecting `python-aioesphomeapi` in Fedora 42, can lead to a denial of service. Exploitation requires the API encryption to be disabled; if encryption is enabled, knowledge of the encryption key is necessary.

Workaround published by Red Hat

To mitigate this issue, enable API encryption with a unique key for each ESPHome device. This prevents unauthenticated denial-of-service attacks by requiring knowledge of the encryption key for exploitation. Refer to ESPHome's Security Best Practices for detailed configuration instructions.

Source: Red Hat security advisory for CVE-2026-23833 (CC BY 4.0)

Frequently Asked Questions

### Summary An integer overflow in the API component's protobuf decoder allows denial-of-service attacks when API encryption is not used. ### Details 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 enabl

O3 Security · Impact-Aware SCA

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