🛡️ CVE-2026-47183 — zeroconf

🟡 CVSS 6.5 — Medium ✅ No Known Exploit CWE-400 NVD
6.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

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

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](https://github.com/python-zeroconf/python-zeroconf/pull/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](https://github.com/python-zeroconf/python-zeroconf/pull/1717), fix
  • [Issue #1714](https://github.com/python-zeroconf/python-zeroconf/issues/1714), public tracking issue
  • [RFC 6762 §17](https://www.rfc-editor.org/rfc/rfc6762#section-17), [RFC 6762 §18](https://www.rfc-editor.org/rfc/rfc6762#section-18), [CWE-400](https://cwe.mitre.org/data/definitions/400.html)

How this vulnerability can be exploited

This issue can be reached from an adjacent network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

Weakness class

CVE-2026-47183 is classified as CWE-400: Uncontrolled Resource Consumption. A request can consume memory, CPU or storage without limit, exhausting capacity for everyone else.

Affected software

CVE-2026-47183 is recorded against 2 packages.

  • unknown
  • zeroconf (fixed in 0.149.6)

Timeline and source

Published on 17 July 2026 and last revised on 23 July 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

github.com
github.com
github.com
github.com
github.com

Details

Severity MEDIUM
CVSS Score 6.5
CVSS Vector CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE CWE-400
Public Exploit ✅ No
Source NVD
Published 2026-07-17
Updated 2026-08-12
Modified 2026-07-23
Fix URL N/A

Affected Packages

Software From version Fixed in
unknown — —
zeroconf — 0.149.6

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