CVE-2026-48487

MEDIUMPre-NVD 6.56.5
EchelonGraph scoreLOW confidence

This medium-severity CVE scores 6.5 under the CNA's CVSS (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: cna:github_m
6.5
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: —CVSS: 6.5Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

zeroconf: Unvalidated rdlength in record payload readers allows LAN-local cache corruption via crafted mDNS packet

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

CVSS v3
6.5
EG Score
6.5(low)
EPSS
—
KEV
Not listed

Published

June 22, 2026

Last Modified

June 22, 2026

Vendor Advisories for CVE-2026-48487(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
zeroconf0.100.0 ... 0.99.0 (259 versions)0.149.16—

Data Freshness Timeline

(refreshed 7× in last 7d / 15× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-06 15:49 UTCEG score recompute
  2. 2026-07-05 16:22 UTCEG score recompute
  3. 2026-07-04 16:51 UTCEG score recompute
  4. 2026-07-03 17:05 UTCEG score recompute
  5. 2026-07-02 17:41 UTCEG score recompute
  6. 2026-07-01 18:13 UTCEG score recompute
  7. 2026-06-30 18:48 UTCEG score recompute
  8. 2026-06-29 19:23 UTCEG score recompute
  9. 2026-06-28 19:59 UTCEG score recompute
  10. 2026-06-27 20:34 UTCEG score recompute
  11. 2026-06-26 21:08 UTCEG score recompute
  12. 2026-06-25 21:44 UTCEG score recompute
  13. 2026-06-24 22:20 UTCEG score recompute
  14. 2026-06-23 22:55 UTCEG score recompute
  15. 2026-06-22 23:31 UTCEG score recompute

Frequently asked(4)

What is CVE-2026-48487?
CVE-2026-48487 is a medium vulnerability published on June 22, 2026. zeroconf: Unvalidated rdlength in record payload readers allows LAN-local cache corruption via crafted mDNS packet Impact readcharacterstring and readstring in src/zeroconf/protocol/incoming.py sliced self.data[self.offset : self.offset + length] and advanced self.offset by the declared length…
When was CVE-2026-48487 disclosed?
CVE-2026-48487 was first published in the National Vulnerability Database on June 22, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
What is the CVSS score of CVE-2026-48487?
CVE-2026-48487 has a CVSS v4.0 base score of 6.5 (CNA self-assessment; NVD's own analysis pending). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-48487?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-48487, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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