{"id":"PYSEC-2026-3435","summary":"python-zeroconf: Unbounded TC-deferred queue allows LAN-local memory exhaustion via spoofed-source flood","details":"### Impact\n\n`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.\n\nAny 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).\n\n### Patches\n\nFixed in `zeroconf` 0.149.12 ([PR #1751](https://github.com/python-zeroconf/python-zeroconf/pull/1751)). Upgrade to `\u003e= 0.149.12`.\n\n### Workarounds\n\nThere 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.\n\n### Resources\n\n- [PR #1751](https://github.com/python-zeroconf/python-zeroconf/pull/1751), fix\n- [RFC 6762 §18.5](https://www.rfc-editor.org/rfc/rfc6762#section-18.5), [CWE-400](https://cwe.mitre.org/data/definitions/400.html)","aliases":["CVE-2026-48045","GHSA-9663-mqmp-p9mm"],"modified":"2026-07-13T16:33:27.758889164Z","published":"2026-07-13T15:46:16.573699Z","references":[{"type":"WEB","url":"https://github.com/python-zeroconf/python-zeroconf/security/advisories/GHSA-9663-mqmp-p9mm"},{"type":"WEB","url":"https://github.com/python-zeroconf/python-zeroconf/pull/1751"},{"type":"WEB","url":"https://github.com/python-zeroconf/python-zeroconf/commit/b22c8ff19c66c68907d220a4823c0950f4fa93f7"},{"type":"PACKAGE","url":"https://github.com/python-zeroconf/python-zeroconf"},{"type":"PACKAGE","url":"https://pypi.org/project/zeroconf"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-9663-mqmp-p9mm"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-48045"}],"affected":[{"package":{"name":"zeroconf","ecosystem":"PyPI","purl":"pkg:pypi/zeroconf"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.149.12"}]}],"versions":["0.100.0","0.101.0","0.102.0","0.103.0","0.104.0","0.105.0","0.106.0","0.107.0","0.108.0","0.109.0","0.110.0","0.111.0","0.112.0","0.114.0","0.115.0","0.115.1","0.115.2","0.116.0","0.117.0","0.118.0","0.118.1","0.119.0","0.120.0","0.121.0","0.122.0","0.122.1","0.122.2","0.122.3","0.123.0","0.124.0","0.125.0","0.126.0","0.127.0","0.128.0","0.128.1","0.128.2","0.128.3","0.128.4","0.128.5","0.129.0","0.130.0","0.131.0","0.132.0","0.132.1","0.132.2","0.133.0","0.134.0","0.135.0","0.136.0","0.136.1","0.136.2","0.137.0","0.137.1","0.137.2","0.138.0","0.138.1","0.139.0","0.14","0.140.0","0.140.1","0.141.0","0.142.0","0.143.0","0.143.1","0.144.0","0.144.1","0.144.2","0.144.3","0.145.0","0.145.1","0.146.0","0.146.1","0.146.2","0.146.3","0.146.4","0.146.5","0.147.0","0.147.1","0.147.2","0.147.3","0.147.4","0.148.0","0.149.0","0.149.1","0.149.10","0.149.11","0.149.2","0.149.3","0.149.4","0.149.5","0.149.6","0.149.7","0.149.8","0.149.9","0.15","0.15.1","0.16.0","0.17.0","0.17.1","0.17.2","0.17.3","0.17.4","0.17.5","0.17.6","0.17.7","0.18.0","0.19.0","0.19.1","0.20.0","0.21.0","0.21.1","0.21.2","0.21.3","0.22.0","0.23.0","0.24.0","0.24.1","0.24.2","0.24.3","0.24.4","0.24.5","0.25.0","0.25.1","0.26.0","0.26.1","0.26.2","0.26.3","0.27.0","0.27.1","0.28.0","0.28.1","0.28.2","0.28.3","0.28.4","0.28.5","0.28.6","0.28.7","0.28.8","0.29.0","0.30.0","0.31.0","0.32.0","0.32.1","0.33.0","0.33.1","0.33.2","0.33.3","0.33.4","0.34.0","0.34.1","0.34.2","0.34.3","0.35.0","0.35.1","0.36.0","0.36.1","0.36.11","0.36.12","0.36.13","0.36.2","0.36.3","0.36.4","0.36.5","0.36.6","0.36.7","0.36.8","0.36.9","0.37.0","0.38.0","0.38.1","0.38.3","0.38.4","0.38.5","0.38.6","0.38.7","0.39.0","0.39.1","0.39.2","0.39.3","0.39.4","0.43.0","0.44.0","0.45.0","0.46.0","0.47.0","0.47.1","0.47.2","0.47.3","0.47.4","0.48.0","0.49.0","0.50.0","0.51.0","0.52.0","0.53.0","0.53.1","0.54.0","0.55.0","0.56.0","0.57.0","0.58.0","0.58.1","0.58.2","0.59.0","0.60.0","0.61.0","0.62.0","0.63.0","0.64.0","0.64.1","0.65.0","0.66.0","0.67.0","0.68.0","0.68.1","0.69.0","0.70.0","0.71.0","0.71.1","0.71.2","0.71.3","0.71.4","0.71.5","0.72.0","0.72.1","0.72.2","0.72.3","0.73.0","0.74.0","0.75.0","0.76.0","0.77.0","0.78.0","0.79.0","0.80.0","0.81.0","0.82.0","0.82.1","0.83.0","0.83.1","0.84.0","0.85.0","0.86.0","0.87.0","0.88.0","0.89.0","0.90.0","0.91.0","0.91.1","0.92.0","0.93.0","0.93.1","0.94.0","0.95.0","0.96.0","0.97.0","0.98.0","0.99.0"],"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/zeroconf/PYSEC-2026-3435.yaml"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}