CVE-2026-47184: Zeroconf Zeroconf Has Unbounded DNS Record Vulnerability
MODERATECVE-2026-47184 is a MODERATE (CVSS 6.5) zeroconf has unbounded dns record vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting Zeroconf libraries in the PyPI ecosystem. The issue involves zeroconf has unbounded dns record cache that allows lan-local memory exhaustion via multicast flood. Remediation is available by upgrading affected packages to version 0.149.7.
CVE-2026-47184 at a Glance
Security Impact
CVSS: 6.5
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
How to Fix CVE-2026-47184
To remediate this vulnerability, upgrade all affected Zeroconf dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
pip install zeroconf>=0.149.7Run the following command in your project directory to verify that all resolved dependencies use the patched release:
pip show zeroconfHow to Check if You Are Affected
To determine whether your Python environment is affected by CVE-2026-47184, inspect your installed packages using pip:
pip show zeroconfAnalyze the terminal output to locate any version of Zeroconf in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.149.7), your application is affected.
Note: The pip show zeroconf command checks currently installed packages in your active Python environment.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-400: Uncontrolled Resource Consumption, where the product does not properly control the allocation and maintenance of a limited resource. In Zeroconf, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2026-47184 Affected Zeroconf Versions
1 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
zeroconf
|
PyPI |
< 0.149.7
|
0.149.7
|
References
Frequently Asked Questions
What is CVE-2026-47184?
Which Zeroconf versions are affected?
What version fixes CVE-2026-47184?
Is zeroconf affected?
What is the CVSS score of CVE-2026-47184?
What CWE is associated with CVE-2026-47184?
How can I check PyPI dependencies for CVE-2026-47184?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-rfg2-pjw2-56x2",
"modified" : "2026-05-29T20:18:53Z",
"published" : "2026-05-29T20:18:53Z",
"aliases" : [ "CVE-2026-47184" ],
"summary" : "zeroconf has unbounded DNS record cache that allows LAN-local memory exhaustion via multicast flood",
"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 §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)",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "PyPI",
"name" : "zeroconf"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "0.149.7"
} ]
} ]
} ],
"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"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-400", "CWE-770" ],
"severity" : "MODERATE",
"github_reviewed" : true,
"github_reviewed_at" : "2026-05-29T20:18:53Z",
"nvd_published_at" : null
}
}