Raw vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-4747 is a high-severity Stack-based Buffer Overflow (CWE-121) vulnerability in Freebsd Freebsd. Its CVSS base score is 8.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique /etc/passwd and /etc/shadow (T1003.008); ranked in the top 35% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-4747 is a stack-based buffer overflow vulnerability (CWE-121) in the RPCSEC_GSS packet validation routine, which copies data from a packet into a stack buffer without ensuring adequate size. This affects the kgssapi.ko kernel module's RPCSEC_GSS implementation in FreeBSD systems, as well as userspace applications that load librpcgss_sec and run RPC servers. The issue allows a malicious client to trigger the overflow without prior authentication. It has a CVSS v3.1 base score of 8.8 (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).
An authenticated user with low privileges (PR:L) can exploit this against a vulnerable FreeBSD NFS server while kgssapi.ko is loaded, sending crafted RPCSEC_GSS packets over the network to achieve remote code execution in the kernel. In userspace, any unauthenticated client able to reach an RPC server using librpcgss_sec can trigger remote code execution, though no such applications are known in the FreeBSD base system.
The FreeBSD security advisory (FreeBSD-SA-26:08.rpcsec_gss.asc) provides details on patches and mitigation. Additional technical publications and a proof-of-concept exploit are available in the referenced GitHub repositories.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-16132
Vulnerability Data
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 2 hardening rules · 2 OS baselines
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Mitigating Controls (NIST 800-53 r5) AI
Developer testing and analysis can discover stack-buffer overflows before deployment.
Input validation directly stops untrusted data from exceeding stack buffer bounds.
Memory-protection mechanisms limit the ability to execute injected code after a stack overflow.
Secure-engineering principles include bounds-checked coding and safe buffer handling that avoid introducing the flaw.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (higher-evidence rows only; rows rated `none` are excluded).
Oracle Linux 8 (1 rule)
- V-248594 OL 8 must implement address space layout randomization (ASLR) to protect its memory from unauthorized code execution. blocks CWE-121
Oracle Linux 9 (1 rule)
- V-271452 OL 9 must use a Linux Security Module configured to enforce limits on system services. blocks CWE-121