PT-2026-45026 · Pypi · Zeroconf
Published
2026-05-29
·
Updated
2026-05-29
·
CVE-2026-47184
CVSS v3.1
6.5
Medium
| Vector | AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
Impact
DNSCache. async add inserted every response record into cache, expirations, expire heap, and service cache with no cap on entry count. The only pre-existing protection was a PTR TTL floor ( DNS PTR MIN TTL = 1125 s, RFC 6762 §10), which actually prolonged attacker-injected records, and a periodic async expire on CACHE CLEANUP INTERVAL = 10 s that could not keep up with a flood.Any unauthenticated host on the local link (UDP/5353,
224.0.0.251 / ff02::fb) can multicast valid mDNS responses with unique names (RFC 6762 §11 allows up to 253 bytes each) and watch them accumulate. On memory-constrained deployments (Home Assistant on Raspberry-Pi-class hardware is the canonical victim) sustained traffic OOM-kills the process; under lighter load, every cache lookup and every periodic expiry pass grows linearly slower, starving asyncio and breaking unrelated zeroconf consumers (discovery, registration, ServiceBrowser callbacks). A second variant — re-multicasting cached records with shifting TTLs — grows expire heap unbounded between cleanup runs without touching cache or total records.Patches
Workarounds
There is no in-process workaround; upgrading is the fix. Otherwise, restrict mDNS (UDP/5353) to trusted Layer-2 segments via AP client isolation, guest-network separation, or host firewall rules.
Resources
- PR #1718, fix
- Issue #1715, public tracking issue
- RFC 6762 §10, RFC 6762 §11, CWE-400
Fix
Allocation of Resources Without Limits
Resource Exhaustion
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Related Identifiers
Affected Products
Zeroconf