Description
Zeroconf is a pure Python implementation of multicast DNS service discovery. Prior to 0.149.6, DNSIncoming._log_exception_debug and the four QuietLogger exception-dedup methods stored an unbounded _seen_logs dictionary keyed by attacker-influenced IncomingDecodeError messages, retaining sys.exc_info() tracebacks whose frame locals kept raw packet self.data buffers and allowing unauthenticated hosts on the local link over UDP/5353 (224.0.0.251 / ff02::fb) to drive memory growth until mDNS-dependent features degrade or the process is OOM-killed. This issue is fixed in version 0.149.6.
Affected products
paulsm: zeroconf
References5
- github.com/python-zeroconf/python-zeroconf/security/advisories/… Vendor AdvisoryPatch
- github.com/python-zeroconf/python-zeroconf/commit/95561e28b2492… Patch
- github.com/python-zeroconf/python-zeroconf/issues/1714 Issue TrackingPatch
- github.com/python-zeroconf/python-zeroconf/pull/1717 Issue TrackingPatch
- github.com/python-zeroconf/python-zeroconf/releases/tag/0.149.6 Release Notes
Metrics
- CVSS 3.1
-
6.5
MEDIUM
Score source: CNA
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - EPSS — exploit probability
- 0% percentile: 34 · as of 14 November 2026
- CWE
- CWE-400
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.