How severe is CVE-2026-47183?

CVE-2026-47183 has a CVSS score of 6.5/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2026-47183?

CVE-2026-47183 affects the following packages: zeroconf (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-47183?

Update zeroconf to 0.149.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-47183 is resolved across your whole dependency graph.

How do I detect CVE-2026-47183 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for zeroconf, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-47183 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2026-47183 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-47183 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-47183?

CVE-2026-47183 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 31th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-47183?

CVE-2026-47183 is classified as Uncontrolled Resource Consumption (CWE-400). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-47183 published, and has it been updated?

CVE-2026-47183 was published on July 17, 2026 and was last updated on August 19, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍

🐍 PyPI

Not in CISA KEV

MEDIUM severity

CVE-2026-47183 — zeroconf

MEDIUMFix: python-zeroconf/python-zeroconf@95561e2

CVE-2026-47183 is a medium-severity (CVSS 6.5) Uncontrolled Resource Consumption vulnerability in zeroconf. A fix is available for zeroconf — see the affected versions and patch details below.

Zeroconf: Unbounded exception-dedup state retains packet buffers via traceback frame locals, enabling LAN-local memory exhaustion

Also known asGHSA-phvx-9mgw-67r5PYSEC-2026-3437

Published

Jul 17, 2026

Updated

Aug 19, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-47183.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs31th percentile — riskier than 31% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-47183 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

🐍zeroconf

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Impact

DNSIncoming._log_exception_debug and the four QuietLogger exception-dedup methods stored an unbounded _seen_logs dict keyed by str(sys.exc_info()[1]). The seven IncomingDecodeError messages raised from _read_name / _decode_labels_at_offset (RFC 6762 §18 name-decoding error paths) all embed self.source — the peer's ephemeral source port, varying per packet — plus byte offset and pointer link, so every attacker-influenced combination produced a fresh dedup key. The stored value was the full sys.exc_info() triple, whose traceback's frame locals retained self.data (the raw inbound packet, up to 8966 bytes per RFC 6762 §17). Each unique malformed packet therefore pinned ~9 KB until process exit.

Any unauthenticated host on the local link (UDP/5353, 224.0.0.251 / ff02::fb) can drive memory growth at line rate; that includes a guest on the same Wi-Fi, a compromised IoT device, or a container on a shared bridge. On memory-constrained deployments (Home Assistant on Raspberry-Pi-class hardware is the canonical victim) sustained traffic trivially OOM-kills the process, and mDNS-dependent features (HomeKit, Chromecast/Matter, AirPlay, printers) degrade or fail.

Patches

Fixed in zeroconf 0.149.6 (PR #1717). 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 #1717, fix
Issue #1714, public tracking issue
RFC 6762 §17, RFC 6762 §18, CWE-400

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`zeroconf`	all versions	0.149.6`pip install --upgrade 'zeroconf==0.149.6'`

Affected Products

1 product · 1 configurations

Application

zeroconfpaulsm

< 0.149.6

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for zeroconf, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update zeroconf to 0.149.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-47183 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Zeroconf is a pure Python implementation of multicast DNS (mDNS) service discovery. Prior to 0.149.6, the exception-deduplication cache that tracks malformed-packet decode errors grows without bound, retaining full tracebacks (including raw packet buffers) keyed by attacker-influenced error messages, leading to…

Workaround published by Red Hat

Upgrade to zeroconf 0.149.6 or later once packaged in the affected Red Hat product. Where upgrading isn't immediately possible, restricting the affected host's exposure to the local network segment (network segmentation or firewalling multicast DNS traffic on UDP/5353) reduces the practical attack surface, since exploitation requires local-link access.

Source: Red Hat security advisory for CVE-2026-47183 (CC BY 4.0)

Frequently Asked Questions

### Impact `DNSIncoming._log_exception_debug` and the four `QuietLogger` exception-dedup methods stored an unbounded `_seen_logs` dict keyed by `str(sys.exc_info()[1])`. The seven `IncomingDecodeError` messages raised from `_read_name` / `_decode_labels_at_offset` (RFC 6762 §18 name-decoding error paths) all embed `self.source` — the peer's ephemeral source port, varying per packet — plus byte `offset` and pointer `link`, so every attacker-influenced combination produced a fresh dedup key. The stored value was the full `sys.exc_info()` triple, whose traceback's frame locals retained `self.data