CVE-2026-48045 python-zeroconf CVE debrief

Who should care

Users of Zeroconf, particularly those using versions prior to 0.149.12, should be aware of this vulnerability and take steps to mitigate it. This includes operators managing affected systems, platform administrators, vulnerability management teams, and security teams responsible for monitoring and incident response.

Technical summary

The AsyncListener.handle_query_or_defer function in Zeroconf retained every truncated TC-bit incoming query, each up to _MAX_MSG_ABSOLUTE = 8966 bytes, in self._deferred[addr] and armed a per-address timer in self._timers[addr] without capping the per-address list or distinct addr keys. This allows unauthenticated hosts on the local link over UDP/5353 (224.0.0.251 / ff02::fb) to spoof sources, grow _deferred and _timers, and cause memory exhaustion and quadratic CPU burn. The issue is fixed in version 0.149.12, which caps the per-address list and distinct addr keys.

Defensive priority

MEDIUM

Recommended defensive actions

• Update Zeroconf to version 0.149.12 or later
• Implement network segmentation to limit the impact of the vulnerability
• Monitor system resources for signs of memory exhaustion and CPU burn
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record was published on 2026-07-17T19:17:15.820Z and has not been modified since then. The NVD entry is currently 6.5 MEDIUM. Evidence is limited to public sources and may not reflect the full scope or impact of the vulnerability. Defenders should verify affected systems and review vendor guidance for specific mitigation steps.

Official resources