Vulnerability Database

352,262

Total vulnerabilities in the database

CVE-2026-47183 — zeroconf

Uncontrolled Resource Consumption

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

CVSS v3:

  • Severity: Medium
  • Score: 6.5
  • AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWEs:

Frequently Asked Questions

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.