{"id":"CVE-2026-47184","aliases":["GHSA-rfg2-pjw2-56x2","PYSEC-2026-3439"],"title":"zeroconf has unbounded DNS record cache that allows LAN-local memory exhaustion via multicast flood","summary":"zeroconf has unbounded DNS record cache that allows LAN-local memory exhaustion via multicast flood","severity":"medium","cvss":6.5,"cvssVector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","vendor":"zeroconf","product":"zeroconf","ecosystem":"pip","affected":["zeroconf < 0.149.7"],"patched":["zeroconf 0.149.7"],"published":"2026-05-29","updated":"2026-07-13","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-rfg2-pjw2-56x2","references":[{"url":"https://github.com/python-zeroconf/python-zeroconf/security/advisories/GHSA-rfg2-pjw2-56x2"},{"url":"https://github.com/python-zeroconf/python-zeroconf/issues/1715"},{"url":"https://github.com/python-zeroconf/python-zeroconf/pull/1718"},{"url":"https://github.com/python-zeroconf/python-zeroconf"}],"tags":["osv","pip"],"ingestedAt":"2026-07-13T18:58:02.705Z","epss":0.00389,"epssPercentile":0.30239,"slug":"CVE-2026-47184","body":"## Overview\n\n### Impact\n\n`DNSCache._async_add` inserted every response record into `cache`, `_expirations`, `_expire_heap`, and `service_cache` with no cap on entry count. The only pre-existing protection was a PTR TTL floor (`_DNS_PTR_MIN_TTL = 1125` s, RFC 6762 §10), which actually *prolonged* attacker-injected records, and a periodic `async_expire` on `_CACHE_CLEANUP_INTERVAL = 10` s that could not keep up with a flood.\n\nAny unauthenticated host on the local link (UDP/5353, `224.0.0.251` / `ff02::fb`) can multicast valid mDNS responses with unique names (RFC 6762 §11 allows up to 253 bytes each) and watch them accumulate. On memory-constrained deployments (Home Assistant on Raspberry-Pi-class hardware is the canonical victim) sustained traffic OOM-kills the process; under lighter load, every cache lookup and every periodic expiry pass grows linearly slower, starving asyncio and breaking unrelated zeroconf consumers (discovery, registration, ServiceBrowser callbacks). A second variant — re-multicasting cached records with shifting TTLs — grows `_expire_heap` unbounded between cleanup runs without touching `cache` or `_total_records`.\n\n### Patches\n\nFixed in `zeroconf` 0.149.6 ([PR #1718](https://github.com/python-zeroconf/python-zeroconf/pull/1718)). Upgrade to `>= 0.149.6`.\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 #1718](https://github.com/python-zeroconf/python-zeroconf/pull/1718), fix\n- [Issue #1715](https://github.com/python-zeroconf/python-zeroconf/issues/1715), public tracking issue\n- [RFC 6762 §10](https://www.rfc-editor.org/rfc/rfc6762#section-10), [RFC 6762 §11](https://www.rfc-editor.org/rfc/rfc6762#section-11), [CWE-400](https://cwe.mitre.org/data/definitions/400.html)\n\n## Affected packages\n\n- `zeroconf < 0.149.7`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `zeroconf 0.149.7`","depth":"sunlit","depthScore":36,"depthScoreParts":{"impact":35.8,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}