# CVE-2026-101303: IPv6 UDP sendto(2) bypasses jail loopback restriction

> Attackers in a FreeBSD jail can bypass network isolation to reach host IPv6 loopback services via UDP.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 15 Oct 2026
- **Updated:** 16 Oct 2026

## What is CVE-2026-101303?

CVE-2026-101303 is a high-severity vulnerability in Freebsd Freebsd, published on 15 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The IPv6 UDP send path for unconnected sockets did not apply the jail policy of rewriting a loopback destination address to the jail's primary IPv6 address.

A process in a classic (non-VNET) jail can send UDP datagrams to services listening on the host's IPv6 loopback address, bypassing jail network isolation.

Weakness: CWE-941 (Incorrectly Specified Destination in a Communication Channel)

## Which versions are affected by CVE-2026-101303?

It affects 1 product.


Products: Freebsd Freebsd.

## How do I fix CVE-2026-101303?

No fix has been published for CVE-2026-101303 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-101303 being exploited?

There is no known exploitation of CVE-2026-101303 in the wild and no public exploit code.

## Other vulnerabilities in Freebsd Freebsd

- [CVE-2018-17160](https://insights.sbomify.com/CVE-2018-17160/): Memory corruption in FreeBSD (critical 10.0)
- [CVE-2014-3954](https://insights.sbomify.com/CVE-2014-3954/): Memory corruption in n/a (critical 10.0)
- [CVE-2006-4304](https://insights.sbomify.com/CVE-2006-4304/): Memory corruption in n/a (critical 10.0)
- [CVE-2006-0226](https://insights.sbomify.com/CVE-2006-0226/): Integer overflow in n/a (critical 10.0)
- [CVE-2004-0002](https://insights.sbomify.com/CVE-2004-0002/): Denial of service in n/a (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-101303 and fix it if it is affected.

What it is: CVE-2026-101303 is a high-severity vulnerability in Freebsd Freebsd, published on 15 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-101303 in the wild and no public exploit code.

Affected product: Freebsd Freebsd. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-101303/ (Markdown: https://insights.sbomify.com/CVE-2026-101303/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-101303
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-101303
- OSV: https://osv.dev/vulnerability/CVE-2026-101303

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-101303/
Summaries are generated and may contain mistakes; the official description above is the record.