Medium [CVE-2026-47183] Denial of Service via unbounded memory growth from mDNS messages
This medium-severity Red Hat Linux advisory covers CVE-2026-47183 affecting Red Hat OpenShift Container Platform 4, Red Hat OpenStack Platform 16.2, Red Hat OpenStack Platform 17.1.
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Summary
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. An unauthenticated attacker on the local network can send specially crafted mDNS messages, causing the system to store an unbounded number of error messages.
This can lead to excessive memory consumption, resulting in a denial of service (DoS) where mDNS-dependent features degrade or the process terminates unexpectedly.
Prior to 0.149.6, the exception-deduplication cache that tracks malformed-packet decode errors grows without bound, retaining full tracebacks (including raw packet buffers) keyed by attacker-influenced error messages, leading to unbounded memory growth, resulting in denial of service impact for unauthenticated hosts on the local network segment (UDP/5353, 224.0.0.251 / ff02::fb).
- < 0.149.6
- < 224.0.0.251
Official advisory · high-confidence parse· fetched 12 days ago·verify at source
- 0.149.6
Official advisory · high-confidence parse· fetched 12 days ago·verify at source
Mitigation checklist
- Upgrade to zeroconf 0.149.6 or later once packaged in the affected Red Hat product. Where upgrading isn't immediately possible, restricting the affected host's exposure to the local network segment (network segmentation or firewalling multicast DNS traffic on UDP/5353) reduces the practical attack surface, since exploitation requires local-link access.
Official advisory · high-confidence parse· fetched 12 days ago·verify at source
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