CVE-2026-4747

Summary

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.

Sources

• CVE-2026-4747Exploit

  Remote kernel RCE exploit for FreeBSD CVE-2026-4747, a stack buffer overflow in kgssapi.ko leading to root shell via ROP chain and shellcode.

• CVE-2026-4747-Exploit

  Remote kernel exploit for FreeBSD CVE-2026-4747, leveraging a stack buffer overflow in kgssapi.ko to achieve RCE with a reverse shell. Includes multi-round ROP delivery and detailed setup instructions.