CVE-2026-48045Medium· 6.5▾ Sunlitpython-zeroconf: Unbounded TC-deferred queue allows LAN-local memory exhaustion via spoofed-source flood
▾ Sunlit zone — Low / medium · no exploitation signal
impact 35.8 · likelihood 0.1 · exploitation 0
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Exploit-prediction probability, daily snapshots since Jul 18.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via GHSA
0.2%
0.2% → 0.4%
AsyncListener.handle_query_or_defer retained every truncated (TC-bit) incoming query in self._deferred[addr] and armed a per-addr timer in self._timers[addr] that flushed the reassembled query within ~500 ms (RFC 6762 §18.5). Neither the per-addr list nor the number of distinct addr keys was capped, and the dedup check (for incoming in reversed(deferred): if incoming.data == msg.data) ran O(N) over the per-addr list on every arrival.
Any unauthenticated host on the local link (UDP/5353, 224.0.0.251 / ff02::fb) can stream byte-distinct TC-flagged mDNS queries — each up to _MAX_MSG_ABSOLUTE = 8966 bytes, with DNSIncoming retaining the raw data buffer plus parsed-record state. Trivially spoofed source IPs multiply the effect across _deferred / _timers, and the O(N) data compare burns CPU quadratically as each per-addr queue grows. On memory-constrained deployments (Home Assistant on Raspberry-Pi-class hardware is the canonical victim) sustained traffic OOM-kills the process; under lighter load, the per-arrival scan and event-loop scheduler starvation break unrelated zeroconf consumers (discovery, registration, ServiceBrowser callbacks).
Fixed in zeroconf 0.149.12 (PR #1751). Upgrade to >= 0.149.12.
There is no in-process workaround; upgrading is the fix. Otherwise, restrict mDNS (UDP/5353) to trusted Layer-2 segments via AP client isolation, guest-network separation, or host firewall rules.
zeroconf < 0.149.12Upgrade to a patched release:
zeroconf 0.149.12Connected by shared product, vendor, weakness, or advisory.
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