# CVE-2026-4747 — FreeBSD

> As of 2026-04-02, CVE-2026-4747 is a HIGH-severity vulnerability in FreeBSD, CVSS v3.1 8.8, EPSS 1.9% (77.4th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-4747, most recently “Claude Mythos / Project Glasswing: Autonomous AI Vulnerability Discovery Compresses the Find-to-Exploit Timeline (CVE-2026-4747 and the AI-Scale Disclosure Problem)”.

**Last updated:** 2026-04-02

## What is 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.

The record classifies CVE-2026-4747 under weakness class [CWE-121](https://intel.threadlinqs.com/cwe/CWE-121). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs low-privilege credentials, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 193 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 8.8 — HIGH (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **EPSS (FIRST):** 1.9% probability of exploitation in the next 30 days, higher than 77.4% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 7.5/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-03-26, last modified 2026-04-02

## Is CVE-2026-4747 being exploited?

No public exploitation evidence for CVE-2026-4747 is recorded in the sources Threadlinqs tracks — CISA KEV, Exploit-DB, public proof-of-concept repositories and ProjectDiscovery Nuclei — as of 2026-04-02. That is an absence of evidence in those feeds, not a guarantee that the vulnerability is unexploited.

## Affected products and versions

- [FreeBSD](https://intel.threadlinqs.com/vendors/freebsd): FreeBSD

## How to fix CVE-2026-4747

Vendor advisory: [https://security.freebsd.org/advisories/FreeBSD-SA-26:08.rpcsec_gss.asc](https://security.freebsd.org/advisories/FreeBSD-SA-26:08.rpcsec_gss.asc). Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

## Threat activity tracking CVE-2026-4747

1 tracked threat in the Threadlinqs corpus references CVE-2026-4747, either in the campaign’s CVE list or as an indicator on the campaign record.

- [Claude Mythos / Project Glasswing: Autonomous AI Vulnerability Discovery Compresses the Find-to-Exploit Timeline (CVE-2026-4747 and the AI-Scale Disclosure Problem)](https://intel.threadlinqs.com/threat/TL-2026-1253) — HIGH · 2026-07-13

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on 2026-07-13. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [security.freebsd.org — vendor advisory](https://security.freebsd.org/advisories/FreeBSD-SA-26:08.rpcsec_gss.asc)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-4747
Full detection coverage and IOCs for threats exploiting CVE-2026-4747 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp