CVE-2026-47184 Zeroconf: Unbounded DNS record cache allows LAN-local memory exhaustion via multicast flood

Medium 6.5 Published 17 Jul 2026 Updated 21 Jul 2026

An attacker on the local network can exhaust memory in the zeroconf library by flooding multicast DNS responses, causing service disruption.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Local or same network only
Victim action needed: Not needed
Fix: Available

What is CVE-2026-47184?

CVE-2026-47184 is a medium-severity denial of service vulnerability in python-zeroconf, published on 17 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

Zeroconf is a pure Python implementation of multicast DNS service discovery. Prior to 0.149.7, DNSCache._async_add inserted every response record into cache, _expirations, _expire_heap, and service_cache without a cap, allowing unauthenticated hosts on the local link over UDP/5353 (224.0.0.251 / ff02::fb) to multicast valid mDNS responses with unique names and cause memory exhaustion, slower cache lookups, slower async_expire passes, and broken discovery, registration, and ServiceBrowser callbacks. This issue is fixed in version 0.149.7.

Weakness: CWE-770

Which versions are affected by CVE-2026-47184?

3 open source packages ship an affected version, including zeroconf. It affects 1 product.

Package	Affected	Fixed in
`zeroconf` PyPI	All versions	`0.149.7`
`zeroconf` PyPI	All versions	`0.149.7`
`zeroconf` PyPI	All versions	`0.149.7`

Products include Paulsm Zeroconf.

How do I fix CVE-2026-47184?

Upgrade zeroconf to 0.149.7 or later.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-47184 being exploited?

There is no known exploitation of CVE-2026-47184 in the wild and no public exploit code.

Sources

Also known as DEBIAN-CVE-2026-47184, GHSA-rfg2-pjw2-56x2, PYSEC-2026-3439, UBUNTU-CVE-2026-47184.