CVE-2026-64823Network attack vector

Cross-site scripting via unvalidated thumbnail MIME type

Published Jul 21, 2026 · Updated Jul 21, 2026

Cross-site scripting in Home Assistant Core before 2026.5.4 allows remote attackers controlling a Shelly device to execute script. The Shelly integration's async_get_media_image() method decodes the device-supplied thumb data URI and returns its bytes and declared MIME type without restricting the content to images. A malicious paired device can therefore serve HTML from the Home Assistant origin, exposing session tokens and permitting authenticated service calls when the proxy response is opened.

CVSS severity2.1
Low
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

Cross-site scripting in Home Assistant Core before 2026.5.4 allows remote attackers controlling a Shelly device to execute script. The Shelly integration's async_get_media_image() method decodes the device-supplied thumb data URI and returns its bytes and declared MIME type without restricting the content to images. A malicious paired device can therefore serve HTML from the Home Assistant origin, exposing session tokens and permitting authenticated service calls when the proxy response is opened.

The record

CVE
CVE-2026-64823
Published
Jul 21, 2026
Updated
Jul 21, 2026
Vendor
Home Assistant
Product
Home Assistant Core
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 21, 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=0 <2026.5.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Home Assistant · Home Assistant Coreversion=0 <2026.5.4

Published CVSS scores

4.7VulnCheckCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N
2.1VulnCheckCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007Command and Scripting Interpreter: JavaScript/JScript

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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