How severe is CVE-2026-48487?

No CVSS score has been assigned to CVE-2026-48487 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-48487?

CVE-2026-48487 affects the following packages: zeroconf (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-48487?

Update zeroconf to 0.149.16 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-48487 is resolved across your whole dependency graph.

How do I detect CVE-2026-48487 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-2026-48487 if there is no patch (or I can't update yet)?

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.

Is CVE-2026-48487 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-48487 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-2026-48487?

CVE-2026-48487 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 39th 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-2026-48487?

CVE-2026-48487 is classified as CWE-130 (CWE-130). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-48487 published, and has it been updated?

CVE-2026-48487 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

CVE-2026-48487 — zeroconf

Fix: python-zeroconf/python-zeroconf@5444495

CVE-2026-48487 is a CWE-130 vulnerability in zeroconf. A fix is available for zeroconf — see the affected versions and patch details below.

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

Also known asGHSA-qc2x-6f54-m6h9PYSEC-2026-3438

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-2026-48487.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs39th percentile — riskier than 39% of all scored CVEsHighest risk

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

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

_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

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`zeroconf`	all versions	0.149.16`pip install --upgrade 'zeroconf==0.149.16'`

Affected Products

1 product · 1 configurations

Application

zeroconfpaulsm

< 0.149.16

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 0.149.16 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-48487 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.

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 0.149.16, the record string/character-string readers advance the parser offset using an attacker-declared RDLENGTH without checking it against the actual buffer length, allowing a malformed TXT, HINFO, or A/AAAA record to…

Workaround published by Red Hat

Upgrade to zeroconf 0.149.16 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-2026-48487 (CC BY 4.0)

Frequently Asked Questions

### 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

O3 Security · Impact-Aware SCA

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