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Medium, CVSS 6.5amended

zeroconf has unbounded DNS record cache that allows LAN-local memory exhaustion via multicast flood

CVE-2026-47184GHSA-rfg2-pjw2-56x2

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (zeroconf 0.149.7), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • PyPI zeroconf

    Affected
    < 0.149.7
    Fixed in
    0.149.7

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
6.5 · CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS
  • CVE-2026-47184: 0.39% estimated exploitation activity in the next 30 days; percentile 33.03 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Impact DNSCache.asyncadd inserted every response record into cache, expirations, expireheap, and servicecache with no cap on entry count. The only pre-existing protection was a PTR TTL floor (DNSPTRMINTTL = 1125 s, RFC 6762 §10), which actually prolonged attacker-injected records, and a periodic asyncexpire on CACHECLEANUPINTERVAL = 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…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-rfg2-pjw2-56x2

  2. Revision 1 · created ·

    Published from osv record GHSA-rfg2-pjw2-56x2

Agent brief

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# Patch Next advisory brief: CVE-2026-47184

Advisory: zeroconf has unbounded DNS record cache that allows LAN-local memory exhaustion via multicast flood
IDs: CVE-2026-47184, GHSA-rfg2-pjw2-56x2
Record: https://patchnext.com/advisories/cve-2026-47184 (revision 2, source checked 26 Oct 2026, 13:41 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: zeroconf 0.149.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI zeroconf: affected < 0.149.7; fixed in 0.149.7

## Suggested inspection (read-only)
- `python -m pip show zeroconf`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on zeroconf.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-rfg2-pjw2-56x2 (OSV record GHSA-rfg2-pjw2-56x2 lists affected ranges: PyPI zeroconf >=0 <0.149.7 (fixed))
- Verified: https://github.com/advisories/GHSA-rfg2-pjw2-56x2 (GitHub-reviewed advisory GHSA-rfg2-pjw2-56x2 lists affected ranges: PyPI zeroconf >=0 <0.149.7)

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