GHSA-qc2x-6f54-m6h9

Suggest an improvement
Source
https://github.com/advisories/GHSA-qc2x-6f54-m6h9
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-qc2x-6f54-m6h9/GHSA-qc2x-6f54-m6h9.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-qc2x-6f54-m6h9
Aliases
  • CVE-2026-48487
Published
2026-06-22T23:07:44Z
Modified
2026-06-22T23:15:40.269928790Z
Severity
  • 6.5 (Medium) CVSS_V3 - CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N CVSS Calculator
  • 4.9 (Medium) CVSS_V4 - CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U CVSS Calculator
Summary
zeroconf: Unvalidated rdlength in record payload readers allows LAN-local cache corruption via crafted mDNS packet
Details

Impact

_read_character_string and _read_string in src/zeroconf/_protocol/incoming.py sliced self.data[self.offset : self.offset + length] and advanced self.offset by the declared length without checking it against self._data_len. Python's slice silently returns fewer bytes when the end index runs past the buffer, so a record whose 16-bit RDLENGTH (RFC 1035 §3.2.1) over-advertised by tens of kilobytes was constructed from a truncated payload, appended to DNSIncoming._answers, and committed to the cache before any later parse failure surfaced. The follow-up _read_name for the next record then failed, but the corrupt record had already entered the answer list and propagated to DNSCache and ServiceInfo.

Any unauthenticated host on the local link (UDP/5353, 224.0.0.251 / ff02::fb) can multicast a single mDNS response carrying a TXT, HINFO, or A/AAAA record that advertises rdlength=65535 and only a handful of real payload bytes; consumers calling ServiceInfo.properties then parse the truncated bytes as if they matched the wire, and downstream integrations (Home Assistant and other zeroconf-driven discovery) trust the decoded record. The bug is parser-state desync rather than RCE, but it seeds the cache with attacker-shaped key/value and address records for a TTL window and is a building block for higher-impact chains.

The impact is likely lower than the other recently released advisories as there is no additional risk of OOM so the severity was manually set to low to override the score CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N (6.5, Medium) since that doesn't fully consider the mDNS threat model.

Patches

Fixed in zeroconf 0.149.16 (PR #1756). Note that this change originally intended to ship in 0.149.13 but we ran out of space on PyPI: see https://github.com/python-zeroconf/python-zeroconf/issues/1769

Upgrade to >= 0.149.16.

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

Database specific 
{
    "github_reviewed_at": "2026-06-22T23:07:44Z",
    "severity": "MODERATE",
    "cwe_ids": [
        "CWE-130"
    ],
    "nvd_published_at": null,
    "github_reviewed": true
}
References

Affected packages

PyPI / zeroconf

Package

Name
zeroconf
View open source insights on deps.dev
Purl
pkg:pypi/zeroconf

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
0.149.16

Affected versions

0.*
0.14
0.15
0.15.1
0.16.0
0.17.0
0.17.1
0.17.2
0.17.3
0.17.4
0.17.5
0.17.6
0.17.7
0.18.0
0.19.0
0.19.1
0.20.0
0.21.0
0.21.1
0.21.2
0.21.3
0.22.0
0.23.0
0.24.0
0.24.1
0.24.2
0.24.3
0.24.4
0.24.5
0.25.0
0.25.1
0.26.0
0.26.1
0.26.2
0.26.3
0.27.0
0.27.1
0.28.0
0.28.1
0.28.2
0.28.3
0.28.4
0.28.5
0.28.6
0.28.7
0.28.8
0.29.0
0.30.0
0.31.0
0.32.0
0.32.1
0.33.0
0.33.1
0.33.2
0.33.3
0.33.4
0.34.0
0.34.1
0.34.2
0.34.3
0.35.0
0.35.1
0.36.0
0.36.1
0.36.2
0.36.3
0.36.4
0.36.5
0.36.6
0.36.7
0.36.8
0.36.9
0.36.11
0.36.12
0.36.13
0.37.0
0.38.0
0.38.1
0.38.3
0.38.4
0.38.5
0.38.6
0.38.7
0.39.0
0.39.1
0.39.2
0.39.3
0.39.4
0.43.0
0.44.0
0.45.0
0.46.0
0.47.0
0.47.1
0.47.2
0.47.3
0.47.4
0.48.0
0.49.0
0.50.0
0.51.0
0.52.0
0.53.0
0.53.1
0.54.0
0.55.0
0.56.0
0.57.0
0.58.0
0.58.1
0.58.2
0.59.0
0.60.0
0.61.0
0.62.0
0.63.0
0.64.0
0.64.1
0.65.0
0.66.0
0.67.0
0.68.0
0.68.1
0.69.0
0.70.0
0.71.0
0.71.1
0.71.2
0.71.3
0.71.4
0.71.5
0.72.0
0.72.1
0.72.2
0.72.3
0.73.0
0.74.0
0.75.0
0.76.0
0.77.0
0.78.0
0.79.0
0.80.0
0.81.0
0.82.0
0.82.1
0.83.0
0.83.1
0.84.0
0.85.0
0.86.0
0.87.0
0.88.0
0.89.0
0.90.0
0.91.0
0.91.1
0.92.0
0.93.0
0.93.1
0.94.0
0.95.0
0.96.0
0.97.0
0.98.0
0.99.0
0.100.0
0.101.0
0.102.0
0.103.0
0.104.0
0.105.0
0.106.0
0.107.0
0.108.0
0.109.0
0.110.0
0.111.0
0.112.0
0.114.0
0.115.0
0.115.1
0.115.2
0.116.0
0.117.0
0.118.0
0.118.1
0.119.0
0.120.0
0.121.0
0.122.0
0.122.1
0.122.2
0.122.3
0.123.0
0.124.0
0.125.0
0.126.0
0.127.0
0.128.0
0.128.1
0.128.2
0.128.3
0.128.4
0.128.5
0.129.0
0.130.0
0.131.0
0.132.0
0.132.1
0.132.2
0.133.0
0.134.0
0.135.0
0.136.0
0.136.1
0.136.2
0.137.0
0.137.1
0.137.2
0.138.0
0.138.1
0.139.0
0.140.0
0.140.1
0.141.0
0.142.0
0.143.0
0.143.1
0.144.0
0.144.1
0.144.2
0.144.3
0.145.0
0.145.1
0.146.0
0.146.1
0.146.2
0.146.3
0.146.4
0.146.5
0.147.0
0.147.1
0.147.2
0.147.3
0.147.4
0.148.0
0.149.0
0.149.1
0.149.2
0.149.3
0.149.4
0.149.5
0.149.6
0.149.7
0.149.8
0.149.9
0.149.10
0.149.11
0.149.12

Database specific

source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-qc2x-6f54-m6h9/GHSA-qc2x-6f54-m6h9.json"