CVE-2026-48045: python-zeroconf Remote Code Execution Vulnerability

MODERATE
Advisory Identifier: GHSA-9663-mqmp-p9mm
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CVSS 6.5
CWE-400 CWE-770
Published
Advisory Summary

CVE-2026-48045 is a MODERATE (CVSS 6.5) remote code execution vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting python-zeroconf libraries in the PyPI ecosystem. The issue involves unbounded tc-deferred queue allows lan-local memory exhaustion via spoofed-source flood. Remediation is available by upgrading affected packages to version 0.149.12.

CVE-2026-48045 at a Glance

CVE Identifier CVE-2026-48045
GHSA Identifier GHSA-9663-mqmp-p9mm
Severity MODERATE
CVSS v3.1 Base Score 6.5
CWE Classification CWE-400: Uncontrolled Resource Consumption
Affected Product python-zeroconf
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 6.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Adjacent (AV:A)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2026-48045

To remediate this vulnerability, upgrade all affected python-zeroconf dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

zeroconf fixed: 0.149.12 
pip install zeroconf>=0.149.12
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show zeroconf

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-48045, inspect your installed packages using pip:

pip show zeroconf

Analyze the terminal output to locate any version of python-zeroconf in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.149.12), your application is affected.

Note: The pip show zeroconf command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-400: Uncontrolled Resource Consumption, where the product does not properly control the allocation and maintenance of a limited resource. In python-zeroconf, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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](https://github.com/python-zeroconf/python-zeroconf/pull/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](https://github.com/python-zeroconf/python-zeroconf/pull/1751), fix - [RFC 6762 §18.5](https://www.rfc-editor.org/rfc/rfc6762#section-18.5), [CWE-400](https://cwe.mitre.org/data/definitions/400.html)

CVE-2026-48045 Affected python-zeroconf Versions

1 component(s)
Fixed Versions:
0.149.12
Product / Package Ecosystem Affected Versions Fixed Version
zeroconf
pypi/zeroconf
PyPI
< 0.149.12
0.149.12

References

GitHub Advisory / Wiki ADVISORY
https://github.com/python-zeroconf/python-zeroconf/security/advisories/GHSA-9663-mqmp-p9mm
python-zeroconf Source Repository REPOSITORY
https://github.com/python-zeroconf/python-zeroconf/pull/1751
Security Fix Commit FIX COMMIT
https://github.com/python-zeroconf/python-zeroconf/commit/b22c8ff19c66c68907d220a4823c0950f4fa93f7
python-zeroconf Source Repository REPOSITORY
https://github.com/python-zeroconf/python-zeroconf

Frequently Asked Questions

What is CVE-2026-48045?
CVE-2026-48045 is a security vulnerability in python-zeroconf involving Unbounded TC-deferred queue allows LAN-local memory exhaustion via spoofed-source flood under CWE-400: Uncontrolled Resource Consumption.
Which python-zeroconf versions are affected?
Affected versions include releases prior to 0.149.12 across affected packages: zeroconf.
What version fixes CVE-2026-48045?
Upgrading to 0.149.12 (or the latest patched release for your respective branch) resolves the vulnerability.
Is zeroconf affected?
Yes, zeroconf is affected in releases prior to 0.149.12. Upgrade your dependency to 0.149.12 or later.
What is the CVSS score of CVE-2026-48045?
CVE-2026-48045 has a CVSS v3.1 base score of 6.5 (MODERATE) with vector string CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2026-48045?
CVE-2026-48045 is classified under CWE-400: Uncontrolled Resource Consumption (The product does not properly control the allocation and maintenance of a limited resource.).
How can I check PyPI dependencies for CVE-2026-48045?
Run the dependency tree command: 'pip show zeroconf'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-9663-mqmp-p9mm",
  "modified" : "2026-06-11T13:28:55Z",
  "published" : "2026-06-11T13:28:55Z",
  "aliases" : [ "CVE-2026-48045" ],
  "summary" : "python-zeroconf: Unbounded TC-deferred queue allows LAN-local memory exhaustion via spoofed-source flood",
  "details" : "### Impact\n\n`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.\n\nAny 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).\n\n### Patches\n\nFixed in `zeroconf` 0.149.12 ([PR #1751](https://github.com/python-zeroconf/python-zeroconf/pull/1751)). Upgrade to `>= 0.149.12`.\n\n### Workarounds\n\nThere 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.\n\n### Resources\n\n- [PR #1751](https://github.com/python-zeroconf/python-zeroconf/pull/1751), fix\n- [RFC 6762 §18.5](https://www.rfc-editor.org/rfc/rfc6762#section-18.5), [CWE-400](https://cwe.mitre.org/data/definitions/400.html)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
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    },
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      } ]
    } ]
  } ],
  "references" : [ {
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  }, {
    "type" : "WEB",
    "url" : "https://github.com/python-zeroconf/python-zeroconf/pull/1751"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/python-zeroconf/python-zeroconf/commit/b22c8ff19c66c68907d220a4823c0950f4fa93f7"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/python-zeroconf/python-zeroconf"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400", "CWE-770" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-11T13:28:55Z",
    "nvd_published_at" : null
  }
}