PYSEC-2026-3439
Vulnerability from pysec - Published: 2026-07-13 15:19 - Updated: 2026-07-13 16:07
VLAI
Details
Impact
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.
Any 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.
Patches
Fixed in zeroconf 0.149.6 (PR #1718). Upgrade to >= 0.149.6.
Workarounds
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.
Resources
- PR #1718, fix
- Issue #1715, public tracking issue
- RFC 6762 §10, RFC 6762 §11, CWE-400
Severity
6.5 (Medium)
Impacted products
| Name | purl | zeroconf | pkg:pypi/zeroconf |
|---|
Aliases
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "zeroconf",
"purl": "pkg:pypi/zeroconf"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.149.7"
}
],
"type": "ECOSYSTEM"
}
],
"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",
"0.149.2",
"0.149.3",
"0.149.4",
"0.149.5",
"0.149.6",
"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"
]
}
],
"aliases": [
"CVE-2026-47184",
"GHSA-rfg2-pjw2-56x2"
],
"details": "### 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 \u00a710), 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 \u00a711 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 \u2014 re-multicasting cached records with shifting TTLs \u2014 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 `\u003e= 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 \u00a710](https://www.rfc-editor.org/rfc/rfc6762#section-10), [RFC 6762 \u00a711](https://www.rfc-editor.org/rfc/rfc6762#section-11), [CWE-400](https://cwe.mitre.org/data/definitions/400.html)",
"id": "PYSEC-2026-3439",
"modified": "2026-07-13T16:07:37.186351Z",
"published": "2026-07-13T15:19:14.814605Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/python-zeroconf/python-zeroconf/security/advisories/GHSA-rfg2-pjw2-56x2"
},
{
"type": "WEB",
"url": "https://github.com/python-zeroconf/python-zeroconf/issues/1715"
},
{
"type": "WEB",
"url": "https://github.com/python-zeroconf/python-zeroconf/pull/1718"
},
{
"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-rfg2-pjw2-56x2"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-47184"
}
],
"severity": [
{
"score": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
],
"summary": "zeroconf has unbounded DNS record cache that allows LAN-local memory exhaustion via multicast flood"
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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