CVE-2026-59178: ESPHome Device Builder: Renamed auth env vars silently disable dashboard authentication on upgrade

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.8%, percentile 55: FIRST’s model estimates a 0.8% chance of exploitation activity in the next 30 days, higher than 55% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes esphome-device-builder (PyPI) < 1.0.12, fixed in 1.0.12. Check your lockfile, including transitive dependencies.

What it is

ESPHome Device Builder Dashboard is a dashboard for the ESPHome home management software. Prior to version 1.0.12, the dashboard reads its authentication credentials from $ESPHOMEUSERNAME and $ESPHOMEPASSWORD. Earlier versions, and the legacy esphome dashboard, read the bare $USERNAME and $PASSWORD instead. When the env vars were renamed the bare names were dropped with no fallback, so an operator who had protected their dashboard with USERNAME / PASSWORD (as the older getting started guide documented) loses authentication on upgrade and the dashboard starts open to anyone who can reach its port. The issue is fixed in 1.0.12. The bare $USERNAME / $PASSWORD are accepted again as a deprecated fallback so previously protected instances stay protected across the upgrade without operator intervention, with a loud deprecation warning at startup directing operators to rename them to $ESPHOMEUSERNAME / $ESPHOMEPASSWORD. The fallback is gated on $PASSWORD being set and is only adopted as a pair, so the OS provided $USERNAME is never read on its own and the original collision footgun stays closed. A lone bare $PASSWORD with no username still fails loud as a credential mismatch rather than starting unauthenticated. This restores compatibility rather than failing closed on the legacy names, because the priority is that an instance which was protected before the upgrade stays protected without the operator having to act; the deprecation warning plus a future removal handles the migration. Operators should migrate to the $ESPHOME names. The esphome container delivers the fix in the 2026.6.2 release, which bumps its pinned esphome-device-builder version to 1.0.12. Without upgrading, restore authentication immediately by setting the new env vars to the same values, on any affected version. Alternatively, do not expose the dashboard port to untrusted networks, and check the startup logs for the WITHOUT AUTHENTICATION banner to confirm whether a given instance is currently open.

From the GitHub advisory

Summary

The dashboard reads its authentication credentials from $ESPHOMEUSERNAME and $ESPHOMEPASSWORD. Earlier versions, and the legacy esphome dashboard, read the bare $USERNAME and $PASSWORD instead. When the env vars were renamed the bare names were dropped with no fallback, so an operator who had protected their dashboard with USERNAME / PASSWORD (as the older getting started guide documented) loses authentication on upgrade and the dashboard starts open to anyone who can reach its port.

Details

Credentials are resolved in DashboardSettings.parseargs. The fallback originally read os.getenv("USERNAME") and os.getenv("PASSWORD"). The env var rename (#265) replaced those with ESPHOMEUSERNAME / ESPHOMEPASSWORD and intentionally removed the bare names, because $USERNAME collides with the OS login user on Linux and Windows and reading it on its own would silently promote the shell user to the dashboard username.

The rename closed that footgun but introduced a backward compatibility break: a deployment that set only the bare names now resolves to no credentials, usingpassword is false, and the REST auth middleware and the WebSocket login gate are both disabled. The process logs a WITHOUT AUTHENTICATION banner at startup, but a container started detached (docker run -d) never surfaces it, so the exposure is silent in practice.

Weakness type: CWE-306.

Product: esphome-device-builder (PyPI) · Assigned by: GitHub_M · Published: 2026-09-14

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.78% probability of exploitation activity in the next 30 days; percentile 55.

Timeline

• 2026-09-14 — CVE record last updated
• 2026-09-14 — CVE record published by GitHub_M
• 2026-09-14 — GitHub-reviewed advisory GHSA-rrxg-g2pf-6hh4 published (critical)

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-rrxg-g2pf-6hh4 github.com
2. CVE.org record CVE-2026-59178 cve.org
3. NVD entry CVE-2026-59178 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com
4. github.com github.com

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