CVE-2026-47184: python-zeroconf memory exhaustion via unbounded DNS cache

CVE-2026-47184 · Severity: medium · CVSS 6.5 · Published 2026-07-17

python-zeroconf is a library used by applications like Home Assistant to discover and register devices on a local network. A vulnerability in how it stores network information allows an attacker on the same local network to flood the system with fake device records. This can lead to the application running out of memory and crashing, or becoming so slow that it can no longer find or manage smart devices, potentially disrupting home automation or office network services.

Technologies: zeroconf (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2026-47184 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-47184 being exploited in the wild.
How severe is CVE-2026-47184?
Medium severity, with a CVSS score of 6.5, published 17 July 2026.
Which products and versions are affected?
zeroconf (PyPI) < 0.149.7, ECOSYSTEM:introduced=0,fixed=0.149.7.
Is there a fix for CVE-2026-47184?
Yes. zeroconf (PyPI): upgrade to 0.149.7 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-47184 attacked?
It is attacked from the adjacent network, in a software library.
Am I affected by CVE-2026-47184?
Check whether you run zeroconf (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • zeroconf (PyPI): upgrade to 0.149.7 or later
    pip install "zeroconf>=0.149.7"

Technical details

A resource exhaustion vulnerability (CWE-770/CWE-400) exists in python-zeroconf's DNSCache component. Prior to version 0.149.7, the `DNSCache._async_add` method inserted incoming mDNS response records into internal data structures (cache, _expirations, _expire_heap, and service_cache) without any upper bound on the number of entries. An unauthenticated attacker on the same local link can multicast valid mDNS responses with unique names over UDP port 5353 to trigger unbounded memory growth. This results in memory exhaustion (OOM), linear performance degradation of cache lookups, and failure of discovery/registration callbacks. The fix introduces a hard cap of 10,000 records (`_MAX_CACHE_RECORDS`) and implements an eviction policy for the oldest records when the limit is reached.

Affected products

  • python-zeroconf python-zeroconf < 0.149.7

Identifiers

  • CVE-2026-47184
  • GHSA-rfg2-pjw2-56x2
  • PYSEC-2026-3439

Timeline

  • 2026-05-17: patched: Fix committed to repository
  • 2026-05-18: disclosed: Issue reported on GitHub
  • 2026-07-17: advisory: CVE-2026-47184 published

References

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