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.
https://github.com/python-zeroconf/python-zeroconf/security/advisories/GHSA-qc2x-6f54-m6h9
https://github.com/python-zeroconf/python-zeroconf/releases/tag/0.149.16
https://github.com/python-zeroconf/python-zeroconf/pull/1756
https://github.com/python-zeroconf/python-zeroconf/issues/1752
https://github.com/python-zeroconf/python-zeroconf/commit/544449596e645fcaad3834fa0cb614a54f847a82
Published: 2026-07-17
Updated: 2026-07-17
Base Score: 6.1
Vector: CVSS2#AV:A/AC:L/Au:N/C:N/I:C/A:N
Severity: Medium
Base Score: 6.5
Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Severity: Medium
Base Score: 5.3
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
Severity: Medium
EPSS: 0.00318