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Vulnerability · Published Jul 17, 2026 · Assigned by GitHub_M

CVE-2026-48487Zeroconf: Unvalidated rdlength in record payload readers allows LAN-local cache corruption via crafted mDNS packet

Medium 5.3

In plain English

A medium-severity security flaw in python-zeroconf from python-zeroconf. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)5.3Medium
Exploit odds (30 days)0.5%top 59.4% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

Zeroconf is a pure Python implementation of multicast DNS service discovery. Prior to 0.149.16, _read_character_string and _read_string in src/zeroconf/_protocol/incoming.py advanced self.offset by attacker-declared RDLENGTH without checking it against self._data_len, allowing unauthenticated hosts on the local link over UDP/5353 (224.0.0.251 / ff02::fb) to send a TXT, HINFO, or A/AAAA record with rdlength=65535 and seed DNSCache and ServiceInfo.properties with truncated, attacker-shaped key/value or address records. This issue is fixed in version 0.149.16.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12python-zeroconfno fix listedDEBIAN-CVE-2026-48487
Debian:13python-zeroconfno fix listedDEBIAN-CVE-2026-48487
Debian:14python-zeroconf0.149.16-1DEBIAN-CVE-2026-48487
PyPIzeroconf0.149.16GHSA-qc2x-6f54-m6h9
PyPIzeroconf0.149.16PYSEC-2026-3438
Ubuntu:22.04:LTSpython-zeroconfno fix listedUBUNTU-CVE-2026-48487
Ubuntu:24.04:LTSpython-zeroconfno fix listedUBUNTU-CVE-2026-48487
Ubuntu:26.04:LTSpython-zeroconfno fix listedUBUNTU-CVE-2026-48487

Affected products (as reported)

VendorProductVersions
python-zeroconf python-zeroconf < 0.149.16

Weakness: CWE-130 · Vector: CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

References