# CVE-2026-47180: Zeroconf: Unbounded recursion in DNS compression-pointer decoder allows LAN-local denial of service

> An attacker on the local network can cause a denial of service in the Zeroconf library by sending crafted mDNS packets that trigger unbounded recursion.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Jul 2026
- **Updated:** 17 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-47180, GHSA-9pgc-3ccv-5297, PYSEC-2026-3436, UBUNTU-CVE-2026-47180

## What is CVE-2026-47180?

CVE-2026-47180 is a medium-severity denial of service vulnerability in python-zeroconf, published on 17 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Zeroconf is a pure Python implementation of multicast DNS service discovery. Prior to 0.149.5, DNSIncoming._decode_labels_at_offset recurses once per DNS-name compression pointer, and a single mDNS packet carrying chained pointers can trigger a RecursionError that escapes DNSIncoming.__init__, causing sustained CPU burn, log flooding, and degraded mDNS-dependent features for unauthenticated hosts on the local link over UDP/5353 (224.0.0.251 / ff02::fb). This issue is fixed in version 0.149.5.

Weakness: CWE-674 (Uncontrolled Recursion)

## Which versions are affected by CVE-2026-47180?

3 open source packages ship an affected version, including zeroconf. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `zeroconf` | PyPI | All versions | 0.149.5 |
| `zeroconf` | PyPI | All versions | 0.149.5 |
| `zeroconf` | PyPI | All versions | 0.149.5 |

Products: Paulsm Zeroconf.

## How do I fix CVE-2026-47180?

Upgrade zeroconf to 0.149.5 or later.

## Is CVE-2026-47180 being exploited?

There is no known exploitation of CVE-2026-47180 in the wild and no public exploit code.

## Other vulnerabilities in python-zeroconf

- [CVE-2026-47183](https://insights.sbomify.com/CVE-2026-47183/): zeroconf: Unbounded exception-dedup state retains packet buffers via traceback frame locals, enabling LAN-local memory exhaustion (medium 6.5)
- [CVE-2026-47184](https://insights.sbomify.com/CVE-2026-47184/): Zeroconf: Unbounded DNS record cache allows LAN-local memory exhaustion via multicast flood (medium 6.5)
- [CVE-2026-48045](https://insights.sbomify.com/CVE-2026-48045/): Zeroconf: Unbounded TC-deferred queue allows LAN-local memory exhaustion via spoofed-source flood (medium 6.5)
- [CVE-2026-48487](https://insights.sbomify.com/CVE-2026-48487/): Zeroconf: Unvalidated rdlength in record payload readers allows LAN-local cache corruption via crafted mDNS packet (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-47180 and fix it if it is affected.

What it is: CVE-2026-47180 is a medium-severity denial of service vulnerability in python-zeroconf, published on 17 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-47180 in the wild and no public exploit code.

Affected packages and fixed versions:
- zeroconf (PyPI): affected all versions; fixed in 0.149.5
- zeroconf (PyPI): affected all versions; fixed in 0.149.5
- zeroconf (PyPI): affected all versions; fixed in 0.149.5

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-47180/ (Markdown: https://insights.sbomify.com/CVE-2026-47180/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-47180
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-47180
- OSV: https://osv.dev/vulnerability/CVE-2026-47180

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-47180/
Summaries are generated and may contain mistakes; the official description above is the record.