# CVE-2026-4747: Remote code execution via RPCSEC_GSS packet validation

> A stack buffer overflow in FreeBSD's RPCSEC_GSS packet validation allows remote code execution in the kernel or userspace RPC servers.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 26 Mar 2026
- **Updated:** 2 Apr 2026
- **Also known as:** GHSA-h63x-7924-m7qf

## What is CVE-2026-4747?

CVE-2026-4747 is a high-severity memory corruption vulnerability in Freebsd Freebsd, published on 26 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Each RPCSEC_GSS data packet is validated by a routine which checks a signature in the packet.  This routine copies a portion of the packet into a stack buffer, but fails to ensure that the buffer is sufficiently large, and a malicious client can trigger a stack overflow.  Notably, this does not require the client to authenticate itself first.

As kgssapi.ko's RPCSEC_GSS implementation is vulnerable, remote code execution in the kernel is possible by an authenticated user that is able to send packets to the kernel's NFS server while kgssapi.ko is loaded into the kernel.

In userspace, applications which have librpcgss_sec loaded and run an RPC server are vulnerable to remote code execution from any client able to send it packets.  We are not aware of any such applications in the FreeBSD base system.

Weakness: CWE-121 (Stack-based Buffer Overflow)

## Which versions are affected by CVE-2026-4747?

It affects 1 product.


Products: Freebsd Freebsd.

## How do I fix CVE-2026-4747?

No fix has been published for CVE-2026-4747 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-4747 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-4747 exists.

Public exploit code:

- https://github.com/kaleth4/CVE-2026-4747- (github_poc): https://github.com/kaleth4/CVE-2026-4747-
- https://github.com/kaleth4/CVE-2026-4747 (github_poc): https://github.com/kaleth4/CVE-2026-4747

## 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-2026-4747 and fix it if it is affected.

What it is: CVE-2026-4747 is a high-severity memory corruption vulnerability in Freebsd Freebsd, published on 26 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-4747 exists.

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-2026-4747/ (Markdown: https://insights.sbomify.com/CVE-2026-4747/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-4747
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-4747
- OSV: https://osv.dev/vulnerability/CVE-2026-4747

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-4747/
Summaries are generated and may contain mistakes; the official description above is the record.