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.
CVE-2026-23833
“—” beside the score: it is equal to NVD's CVSS score.
This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.3% (22nd percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.
Also known asEUVD-2026-3306 (ENISA EUVD) · GHSA-4h3h-63v6-88qx (GitHub Security Advisories)Source: ENISA EUVD
- CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
A fix is available — apply it.
- CVSS v3
- 7.5
- EG Score
- 7.5HIGHmedium confidence
- EG Risk
- 65EG Risk 65/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity75% × 45%Impact severity (EG Severity): CVSS 7.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation40% × 40%EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.Automatability100% × 15%CISA's SSVC Automatable value: yes (Vulnrichment).SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high. - EPSS PROB
- 0.3%
- EPSS %ILE
- 22nd
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (7.5): severity, escalated by confirmed exploitation. This CVE's 7.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.5 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
- EG Likelihood
- 0.3% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-31). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
January 19, 2026
Last Modified
June 17, 2026
Advisory Details (4)
Auto-updated Aug 2, 2026Denial-of-service via out-of-bounds check bypass in the API component · Advisory · esphome/esphome · GitHub
https://github.com/esphome/esphome/security/advisories/GHSA-4h3h-63v6-88qx[api] Use subtraction for protobuf bounds checking
Patch available: esphome/esphome 2026.4.2 (PR #13306 merged 2026-01-17)
https://github.com/esphome/esphome/pull/13306commit 69d7b6e92103 (esphome/esphome)
Patch available: esphome/esphome 2026.4.2 (contains commit 69d7b6e92103)
https://github.com/esphome/esphome/commit/69d7b6e9210390051318bd8e6410727689de08d6Security Best Practices - ESPHome - Smart Home Made Simple
https://esphome.io/guides/security_best_practicesPatch Availability(1)
| Vendor / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| pip | esphome @ 2025.12.7 (fixes >= 2025.9.0, < 2025.12.7) | — | ghsa |
Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.
Affected Packages
(1 across 1 ecosystem)
PyPI(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| esphome | 2025.10.0 ... 2025.9.3 (37 versions) |
| — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 9× in last 7d / 39× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
Showing the most recent 99 of 203 refreshes on record for this CVE.
A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 1 repeat row among the latest 100 is merged into the row it repeats. The 104 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-11-01 07:57 UTCGHSA enrichmentGHSA-4h3h-63v6-88qx · GitHub severity MODERATE
- 2026-11-01 07:57 UTCEG score recompute
- 2026-10-31 16:32 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-10-30 20:24 UTCEG score recompute
- 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-10-29 16:32 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-10-28 16:31 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-10-27 16:31 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
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- 2026-10-25 16:32 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-10-25 14:41 UTCEG score recompute
- 2026-10-24 16:32 UTCEPSS rescoreEPSS 0.3% · 21st percentile
- 2026-10-24 06:45 UTCEG score recompute
- 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.3% · 21st percentile
- 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.3% · 21st percentile
- 2026-10-21 16:32 UTCEPSS rescoreEPSS 0.3% · 21st percentile
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- 2026-10-19 16:31 UTCEPSS rescoreEPSS 0.3% · 21st percentile
- 2026-10-18 03:54 UTCEG score recompute
- 2026-10-17 17:04 UTCEG score recompute
- 2026-10-17 16:33 UTCEPSS rescoreEPSS 0.3% · 21st percentile
- 2026-10-16 16:41 UTCEPSS rescoreEPSS 0.3% · 21st percentile
- 2026-10-15 16:31 UTCEPSS rescoreEPSS 0.3% · 21st percentile
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- 2026-10-13 16:33 UTCEPSS rescoreEPSS 0.3% · 21st percentile
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- 2026-10-12 16:20 UTCEG score recompute
- 2026-10-11 20:02 UTCEG score recompute
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- 2026-10-11 14:47 UTCEG score recompute
- 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.3% · 21st percentile
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- 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.3% · 21st percentile
- 2026-10-08 20:28 UTCOSV refresh
- 2026-10-08 17:11 UTCEPSS rescoreEPSS 0.3% · 21st percentile
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- 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
- 2026-09-19 03:00 UTCOSV refresh
- 2026-09-18 19:27 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
- 2026-09-16 14:07 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
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- 2026-08-31 06:25 UTCOSV refresh
- 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.3% · 20th percentile
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- 2026-08-25 13:48 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.3% · 21st percentile
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- 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.3% · 21st percentile
- 2026-08-19 17:03 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-08-18 13:48 UTCEPSS rescoreEPSS 0.3% · 20th percentile
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- 2026-08-15 01:30 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-08-14 13:44 UTCEG score recompute
- 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.3% · 19th percentile
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- 2026-08-11 00:00 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-08-09 19:20 UTCEG score recompute
- 2026-08-09 13:46 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-08-08 16:37 UTCEPSS rescoreEPSS 0.3% · 19th percentile
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- 2026-08-06 13:46 UTCEPSS rescoreEPSS 0.3% · 19th percentile
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- 2026-07-26 14:54 UTCEPSS rescoreEPSS 0.3% · 19th percentile
Related CVEs(same product + same CWE)
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5 shownPyPI:esphome
Frequently asked(5)
What is CVE-2026-23833?
When was the CVE record for CVE-2026-23833 published?
Is CVE-2026-23833 actively exploited?
What is the CVSS score of CVE-2026-23833?
How do I remediate CVE-2026-23833?
Dependency Blast Radius
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