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CVE-2026-48045VulnerabilityPublished Updated

esphome · python-zeroconf: Unbounded TC-deferred queue allows LAN-local memory exhaustion via spoofed-source flood

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 `AsyncListener.handle_query_or_defer` retained every truncated (TC-bit) incoming query in `self._deferred[addr]` and armed a per-addr timer in `self._timers[addr]` that flushed the reassembled query within ~500 ms (RFC 6762 §18.5). Neither the per-addr list nor the number of distinct `addr` keys was capped, and the dedup check (`for incoming in reversed(deferred): if incoming.data == msg.data`) ran O(N) over the per-addr list on every arrival. Any unauthenticated host on the local link (UDP/5353, `224.0.0.251` / `ff02::fb`) can stream byte-distinct TC-flagged mDNS queries — each up to `_MAX_MSG_ABSOLUTE = 8966` bytes, with `DNSIncoming` retaining the raw `data` buffer plus parsed-record state. Trivially spoofed source IPs multiply the effect across `_deferred` / `_timers`, and the O(N) data compare burns CPU quadratically as each per-addr queue grows. On memory-constrained deployments (Home Assistant on Raspberry-Pi-class hardware is the canonical victim) sustained traffic OOM-kills the process; under lighter load, the per-arrival scan and event-loop scheduler starvation break unrelated zeroconf consumers (discovery, registration, ServiceBrowser callbacks). ### Patches Fixed in `zeroconf` 0.149.12 ([PR #1751](https://github.com/python-zeroconf/python-zeroconf/pull/1751)). Upgrade to `>= 0.149.12`. ### 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 #1751](https://github.com/python-zeroconf/python-zeroconf/pull/1751), fix - [RFC 6762 §18.5](https://www.rfc-editor.org/rfc/rfc6762#section-18.5), [CWE-400](https://cwe.mitre.org/data/definitions/400.html)

References

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