FreeBSD Kernel kgssapi.ko RPCSEC_GSS Stack Buffer Overflow
CVE-2026-4747 Published on March 26, 2026
Remote code execution via RPCSEC_GSS packet validation
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.
Vulnerability Analysis
CVE-2026-4747 can be exploited with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to be very high.
Weakness Type
What is a Stack Overflow Vulnerability?
A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).
CVE-2026-4747 has been classified to as a Stack Overflow vulnerability or weakness.
Products Associated with CVE-2026-4747
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Affected Versions
FreeBSD:- Version 15.0-RELEASE and below p5 is affected.
- Version 14.4-RELEASE and below p1 is affected.
- Version 14.3-RELEASE and below p10 is affected.
- Version 13.5-RELEASE and below p11 is affected.