CVE-2026-4747: FreeBSD remote code execution (CVSS 8.8)

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.

CVSS 3.1 breakdown

Attack vectorNetwork

Attack complexityLow

Privileges requiredLow

User interactionNone

ScopeUnchanged

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

FreeBSD13.5 · 14.3 · 14.4 · 15.0

Remediation

No fixed version is recorded in the NVD data. Check the vendor advisory for the latest guidance.

Patch & vendor advisories

https://security.freebsd.org/advisories/FreeBSD-SA-26:08.rpcsec_gss.asc

References

https://github.com/califio/publications/blob/main/MADBugs/CVE-2026-4747/exploit.pyExploit
https://github.com/califio/publications/tree/main/MADBugs/CVE-2026-4747ExploitThird Party Advisory
https://security.freebsd.org/advisories/FreeBSD-SA-26:08.rpcsec_gss.ascVendor Advisory

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2026-4747 being actively exploited?

CVE-2026-4747 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 1.11%.

How severe is CVE-2026-4747?

CVE-2026-4747 has a CVSS 3.1 base score of 8.8, rated high. EPSS estimates a 1.11% probability of exploitation.

Which products are affected by CVE-2026-4747?

Affected products include FreeBSD.

How do I fix CVE-2026-4747?

Apply the vendor's patch or advisory guidance, then verify no affected versions remain across your devices.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-4747 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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