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CVE-2026-47180VulnerabilityPublished Updated

Esphome: zeroconf has unbounded recursion

Affects esphomeSource GCVE Database

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Not known to be exploited · CVSS 6.5 Medium : upgrade to 2026.5.0 when convenient.

Data as of 30 Oct 2026, 07:30 UTC

CVSS 3.1 base score
6.5Medium
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 2026.5.0
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 13 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade esphome to 2026.5.0.

Affected software

ProductAffectedFixed in
Homebrewesphomepkg:brew/esphomeOther threatsAffected
  • >=2022.1.2 <2026.5.0
Fixed in
  • 2026.5.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

### Impact `DNSIncoming._decode_labels_at_offset` recurses once per DNS-name compression pointer (RFC 1035 §4.1.4). Pointer cycles and label counts were capped, but the chain length of unique forward pointers was not. A single ~3 kB mDNS packet carrying ~1500 chained pointers drives the recursion past CPython's default limit, and `RecursionError` was not listed in `DECODE_EXCEPTIONS`, so it escaped `DNSIncoming.__init__` and was logged by asyncio's default exception handler. Any unauthenticated host on the local link (UDP/5353, `224.0.0.251` / `ff02::fb`) can degrade the mDNS listener; that includes a guest on the same Wi-Fi, a compromised IoT device, or a container on a shared bridge. Replaying at a few hertz produces sustained CPU burn and log flooding, and mDNS-dependent features (HomeKit, Chromecast/Matter, AirPlay, printers) degrade while the attack is in flight. ### Patches Fixed in `zeroconf` 0.149.5 ([PR #1719](https://github.com/python-zeroconf/python-zeroconf/pull/1719)). Upgrade to `>= 0.149.5`. ### Workarounds There is no in-process workaround; upgrading is the fix. Otherwise, restrict mDNS (UDP/5353) to trusted Layer-2 segments via AP client isolation, guest-network separation, or host firewall rules. ### Resources - [PR #1719](https://github.com/python-zeroconf/python-zeroconf/pull/1719), fix - [Issue #1713](https://github.com/python-zeroconf/python-zeroconf/issues/1713), public tracking issue - [RFC 1035 §4.1.4](https://www.rfc-editor.org/rfc/rfc1035#section-4.1.4), [RFC 6762](https://www.rfc-editor.org/rfc/rfc6762), [CWE-674](https://cwe.mitre.org/data/definitions/674.html)

References

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