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
paulsm: zeroconf
References4
- github.com/python-zeroconf/python-zeroconf/security/advisories/… Vendor AdvisoryPatch
- github.com/python-zeroconf/python-zeroconf/commit/b22c8ff19c66c… Patch
- github.com/python-zeroconf/python-zeroconf/pull/1751 Issue TrackingPatch
- github.com/python-zeroconf/python-zeroconf/releases/tag/0.149.12 Release Notes
Metrics
- CVSS 3.1
-
6.5
MEDIUM
Score source: CNA
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - EPSS — exploit probability
- 0% percentile: 31 · as of 14 November 2026
- CWE
- CWE-770
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