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

High 8.8 Published 26 Mar 2026 Updated 2 Apr 2026

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

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

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

Which versions are affected by CVE-2026-4747?

It affects 1 product.

Products include 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.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

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: 2 proofs of concept on GitHub.

All Freebsd Freebsd vulnerabilities

Sources

Also known as GHSA-h63x-7924-m7qf.