How severe is CVE-2026-48045?

CVE-2026-48045 has a CVSS score of 6.5/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2026-48045?

CVE-2026-48045 affects the following packages: zeroconf (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-48045?

Update zeroconf to 0.149.12 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-48045 is resolved across your whole dependency graph.

How do I detect CVE-2026-48045 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for zeroconf, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-48045 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2026-48045 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-48045 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-48045?

CVE-2026-48045 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 30th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-48045?

CVE-2026-48045 is classified as CWE-770 (CWE-770). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-48045 published, and has it been updated?

CVE-2026-48045 was published on July 17, 2026 and was last updated on October 21, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍

🐍 PyPI

Not in CISA KEV

MEDIUM severity

CVE-2026-48045 — zeroconf

MEDIUMFix: python-zeroconf/python-zeroconf@b22c8ff

CVE-2026-48045 is a medium-severity (CVSS 6.5) CWE-770 vulnerability in zeroconf. A fix is available for zeroconf — see the affected versions and patch details below.

Zeroconf: Unbounded TC-deferred queue allows LAN-local memory exhaustion via spoofed-source flood

Also known asGHSA-9663-mqmp-p9mmPYSEC-2026-3435

Published

Jul 17, 2026

Updated

Oct 21, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 23, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

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 CVE-2026-48045.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs30th percentile — riskier than 30% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-48045 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 394,803 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

🐍zeroconf

Real-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

AsyncListener.handle_query_or_defer retained every truncated (TC-bit) incoming query in self._deferred[addr] and armed a per-addr timer in self._timers[addr] that flushed the reassembled query within ~500 ms (RFC 6762 §18.5). Neither the per-addr list nor the number of distinct addr keys was capped, and the dedup check (for incoming in reversed(deferred): if incoming.data == msg.data) ran O(N) over the per-addr list on every arrival.

Any unauthenticated host on the local link (UDP/5353, 224.0.0.251 / ff02::fb) can stream byte-distinct TC-flagged mDNS queries — each up to _MAX_MSG_ABSOLUTE = 8966 bytes, with DNSIncoming retaining the raw data buffer plus parsed-record state. Trivially spoofed source IPs multiply the effect across _deferred / _timers, and the O(N) data compare burns CPU quadratically as each per-addr queue grows. On memory-constrained deployments (Home Assistant on Raspberry-Pi-class hardware is the canonical victim) sustained traffic OOM-kills the process; under lighter load, the per-arrival scan and event-loop scheduler starvation break unrelated zeroconf consumers (discovery, registration, ServiceBrowser callbacks).

Patches

Fixed in zeroconf 0.149.12 (PR #1751). Upgrade to >= 0.149.12.

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 #1751, fix
RFC 6762 §18.5, CWE-400

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`zeroconf`	all versions	0.149.12`pip install --upgrade 'zeroconf==0.149.12'`

Affected Products

1 product · 1 configurations

Application

zeroconfpaulsm

< 0.149.12

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for zeroconf, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update zeroconf to 0.149.12 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-48045 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Zeroconf is a pure Python implementation of multicast DNS (mDNS) service discovery. Prior to 0.149.12, truncated (TC-bit) incoming queries are retained per source address with a per-address timer armed, but neither the deferred query list nor the number of distinct addresses is capped, allowing memory and timer…

Workaround published by Red Hat

Upgrade to zeroconf 0.149.12 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.

Source: Red Hat security advisory for CVE-2026-48045 (CC BY 4.0)

Frequently Asked Questions

### Impact `AsyncListener.handle_query_or_defer` retained every truncated (TC-bit) incoming query in `self._deferred[addr]` and armed a per-addr timer in `self._timers[addr]` that flushed the reassembled query within ~500 ms (RFC 6762 §18.5). Neither the per-addr list nor the number of distinct `addr` keys was capped, and the dedup check (`for incoming in reversed(deferred): if incoming.data == msg.data`) ran O(N) over the per-addr list on every arrival. Any unauthenticated host on the local link (UDP/5353, `224.0.0.251` / `ff02::fb`) can stream byte-distinct TC-flagged mDNS queries — each u