Zeroconf: Unbounded DNS record cache allows LAN-local memory exhaustion via multicast flood
Key facts
- Attack vector
- Adjacent network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 4 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-770.
Summary
Zeroconf is a pure Python implementation of multicast DNS service discovery. Prior to 0.149.7, DNSCache._async_add inserted every response record into cache, _expirations, _expire_heap, and service_cache without a cap, allowing unauthenticated hosts on the local link over UDP/5353 (224.0.0.251 / ff02::fb) to multicast valid mDNS responses with unique names and cause memory exhaustion, slower cache lookups, slower async_expire passes, and broken discovery, registration, and ServiceBrowser callbacks. This issue is fixed in version 0.149.7.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| python-zeroconf | python-zeroconf | before 0.149.7 | 0.149.7 | Patch available | CNA |
| — | zeroconf (PyPI) | before 0.149.7 | 0.149.7 | Patch available | GHSA-rfg2-pjw2-56x2 |
- python-zeroconf Vendorpython-zeroconf Affected before 0.149.7 Fixed in 0.149.7 Patch available CNA
- zeroconf (PyPI) Vendor— Affected before 0.149.7 Fixed in 0.149.7 Patch available GHSA-rfg2-pjw2-56x2
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:paulsm:zeroconf:*:*:*:*:*:python:*:* | before 0.149.7 | Vulnerable | python-zeroconf |
- cpe:2.3:a:paulsm:zeroconf:*:*:*:*:*:python:*:* Versions before 0.149.7 Vulnerable ·python-zeroconf
Remediation
- Fix · CNA python-zeroconf (python-zeroconf) Fixed in 0.149.7
- Fix · GHSA-rfg2-pjw2-56x2 zeroconf (PyPI) Fixed in 0.149.7 Advisory →
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet: Fix deferred |
| Red Hat OpenStack Platform 16.2 | Affected | No fix planned: Out of support scope |
| Red Hat OpenStack Platform 17.1 | Affected | No fix planned: Out of support scope |
| Red Hat OpenStack Platform 18.0 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-47184
- 2026-10-03 Alias added: GHSA-rfg2-pjw2-56x2
References
Patch 4
- https://github.com/python-zeroconf/python-zeroconf/security/advisories/GHSA-rfg2-pjw2-56x2
- https://github.com/python-zeroconf/python-zeroconf/issues/1715
- https://github.com/python-zeroconf/python-zeroconf/pull/1718
- https://github.com/python-zeroconf/python-zeroconf/commit/0ad3f37b5b852b8f614d322283d148efb2cef6e4
More python-zeroconf Zeroconf vulnerabilities
- TI-2026-35487 Zeroconf: Unbounded TC-deferred queue allows LAN-local memory exhaustion via spoofed-source flood CVSS 3.1MEDIUM 6.5
- TI-2026-34772 Uncontrolled resource consumption in python-zeroconf CVSS 3.1MEDIUM 6.5
- TI-2026-34769 Zeroconf: Unbounded recursion in DNS compression-pointer decoder allows LAN-local denial of service CVSS 3.1MEDIUM 6.5
- TI-2026-35849 Zeroconf: Unvalidated rdlength in record payload readers allows LAN-local cache corruption via crafted mDNS packet CVSS 4.0MEDIUM 5.3
Sources
- CVE-2026-47184 · CVE Program
- CVE-2026-47184 · NVD
- FIRST EPSS
- GHSA-rfg2-pjw2-56x2 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-47184 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences