Buffer overflow in FreeBSD

CVE-2026-4747

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 class: Buffer Overflow

Published · last modified .

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.011 (64.7th percentile), scored .

Low probability of exploitation in the next 30 days, but still tracked. 65th percentile — 64.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-4747: fell from 0.025 to 0.011.

EPSS over last 30 days · oldest: 0.025 · newest: 0.011 · change: -0.014

Affected products

  • FreeBSD — versions 14.3, 13.5, 15.0

Weakness classification (CWE)

Public proof-of-concept exploits

References

Frequently asked questions

What is CVE-2026-4747?
CVE-2026-4747 is a high-severity vulnerability in FreeBSD, classified under Stack-based Buffer Overflow. CVSS score: 8.8/10. Published 2026-03-26.
How severe is CVE-2026-4747?
High severity. CVSS v3 base score is 8.8 out of 10.
Is CVE-2026-4747 known to be exploited?
2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.