What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-17 · updated 2026-08-17
• Weakness: CWE-770

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.

Affected products

• python-zeroconf: before 0.149.7 — fixed in 0.149.7

How to fix

Upgrade to a fixed version: python-zeroconf 0.149.7. Check the vendor advisory for mitigations.

References

• https://github.com/python-zeroconf/python-zeroconf/commit/0ad3f37b5b852b8f614d322283d148efb2cef6e4
• https://github.com/python-zeroconf/python-zeroconf/issues/1715
• https://github.com/python-zeroconf/python-zeroconf/pull/1718
• https://github.com/python-zeroconf/python-zeroconf/releases/tag/0.149.7
• https://github.com/python-zeroconf/python-zeroconf/security/advisories/GHSA-rfg2-pjw2-56x2

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