What’s Vulnerable › Vulnerabilities

CVE-2026-47180: Zeroconf: Unbounded recursion in DNS compression-pointer decoder allows LAN-local denial of service

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-17 · updated 2026-08-17
• Weakness: CWE-674

Description

Zeroconf is a pure Python implementation of multicast DNS service discovery. Prior to 0.149.5, DNSIncoming._decode_labels_at_offset recurses once per DNS-name compression pointer, and a single mDNS packet carrying chained pointers can trigger a RecursionError that escapes DNSIncoming.__init__, causing sustained CPU burn, log flooding, and degraded mDNS-dependent features for unauthenticated hosts on the local link over UDP/5353 (224.0.0.251 / ff02::fb). This issue is fixed in version 0.149.5.

Affected products

• python-zeroconf: before 0.149.5 — fixed in 0.149.5

How to fix

Upgrade to a fixed version: python-zeroconf 0.149.5. Check the vendor advisory for mitigations.

References

• https://github.com/python-zeroconf/python-zeroconf/commit/f9e23592137f30fdf7ef710dba065da31c79b1cf
• https://github.com/python-zeroconf/python-zeroconf/pull/1719
• https://github.com/python-zeroconf/python-zeroconf/releases/tag/0.149.5
• https://github.com/python-zeroconf/python-zeroconf/security/advisories/GHSA-9pgc-3ccv-5297

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