GHSA-rfg2-pjw2-56x2 is a medium-severity (CVSS 6.5) CWE-770 vulnerability in zeroconf. O3 Security confirms whether GHSA-rfg2-pjw2-56x2 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
zeroconf has unbounded DNS record cache that allows LAN-local memory exhaustion via multicast flood
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-rfg2-pjw2-56x2.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-rfg2-pjw2-56x2 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 365,017 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
zeroconfReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
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
Fixed in zeroconf 0.149.6 (PR #1718). Upgrade to >= 0.149.6.
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
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | zeroconf | all versions | 0.149.7 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for zeroconf. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update zeroconf to 0.149.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-rfg2-pjw2-56x2 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-rfg2-pjw2-56x2 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-rfg2-pjw2-56x2. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-rfg2-pjw2-56x2 in your dependencies?
O3 detects GHSA-rfg2-pjw2-56x2 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.