Skip to content
Fencer Vulns
no cvss —

CVE-2025-40004 json

net/9p: Fix buffer overflow in USB transport layer

published 2025-10-20 12 mo ago modified 2026-10-19 20 d ago also EUVD-2025-35036

cvss
—
not scored
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 18%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

net/9p: Fix buffer overflow in USB transport layer

A buffer overflow vulnerability exists in the USB 9pfs transport layer where inconsistent size validation between packet header parsing and actual data copying allows a malicious USB host to overflow heap buffers.

The issue occurs because: - usb9pfs_rx_header() validates only the declared size in packet header - usb9pfs_rx_complete() uses req->actual (actual received bytes) for memcpy

This allows an attacker to craft packets with small declared size (bypassing validation) but large actual payload (triggering overflow in memcpy).

Add validation in usb9pfs_rx_complete() to ensure req->actual does not exceed the buffer capacity before copying data.

Patch / fix

  • Linux Linux 6.12.53, 6.17.3, 6.18
  • linux Debian 13 6.12.57-1
  • linux Debian 14 6.17.6-1

debian advisories DEBIAN-CVE-2025-40004

  • linux Ubuntu 25.10 6.17.0-14.14
  • linux-aws Ubuntu 25.10 6.17.0-1007.7
  • linux-gcp Ubuntu 25.10 6.17.0-1007.7
  • linux-azure Ubuntu 25.10 6.17.0-1008.8
  • linux-raspi Ubuntu 25.10 6.17.0-1008.8
  • linux-riscv Ubuntu 25.10 6.17.0-14.14.1
  • linux-oracle Ubuntu 25.10 6.17.0-1007.7
  • linux-aws-6.17 Ubuntu 24.04 LTS 6.17.0-1007.7~24.04.1

ubuntu advisories UBUNTU-CVE-2025-40004

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel-source-longterm openSUSE Tumbleweed 6.18.16-1.1
  • kernel-source openSUSE Tumbleweed 6.17.5-1.1

opensuse advisories openSUSE-SU-2026:10301-1openSUSE-SU-2025:15671-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-40004 updated

kernel: net/9p: Fix buffer overflow in USB transport layer

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.27% chance of exploitation in the next 30 days, higher than 18% of all scored CVEs (FIRST EPSS, 2026-11-08).

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.