What’s Vulnerable › Vulnerabilities

CVE-2026-48045: Zeroconf: Unbounded TC-deferred queue allows LAN-local memory exhaustion via spoofed-source 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 0.149.12, AsyncListener.handle_query_or_defer retained every truncated TC-bit incoming query, each up to _MAX_MSG_ABSOLUTE = 8966 bytes, in self._deferred[addr] and armed a per-address timer in self._timers[addr] without capping the per-address list or distinct addr keys, allowing unauthenticated hosts on the local link over UDP/5353 (224.0.0.251 / ff02::fb) to spoof sources, grow _deferred and _timers, and cause memory exhaustion and quadratic CPU burn. This issue is fixed in version 0.149.12.

Affected products

• python-zeroconf: before 0.149.12 — fixed in 0.149.12

How to fix

Upgrade to a fixed version: python-zeroconf 0.149.12. Check the vendor advisory for mitigations.

References

• https://github.com/python-zeroconf/python-zeroconf/commit/b22c8ff19c66c68907d220a4823c0950f4fa93f7
• https://github.com/python-zeroconf/python-zeroconf/pull/1751
• https://github.com/python-zeroconf/python-zeroconf/releases/tag/0.149.12
• https://github.com/python-zeroconf/python-zeroconf/security/advisories/GHSA-9663-mqmp-p9mm

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