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Fencer Vulns
critical 9.8

CVE-2025-37879 in the critical feed json

9p/net: fix improper handling of bogus negative read/write replies

published 2025-05-09 18 mo ago modified 2026-08-05 3 mo ago also EUVD-2025-14111

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 54%
public exploits
0
none known

Summary

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

9p/net: fix improper handling of bogus negative read/write replies

In p9_client_write() and p9_client_read_once(), if the server incorrectly replies with success but a negative write/read count then we would consider written (negative) <= rsize (positive) because both variables were signed.

Make variables unsigned to avoid this problem.

The reproducer linked below now fails with the following error instead of a null pointer deref: 9pnet: bogus RWRITE count (4294967295 > 3)

Patch / fix

  • Linux Linux 6.1.136, 6.6.89, 6.12.26, 6.14.5, 6.15
  • linux Debian 12 6.1.137-1
  • linux Debian 14, Debian 13 6.12.27-1

debian advisories DEBIAN-CVE-2025-37879

  • linux Ubuntu 24.04 LTS 6.8.0-100.100
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1046.49
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1047.50
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1043.48
  • linux-ibm Ubuntu 24.04 LTS 6.8.0-1044.44
  • linux-azure Ubuntu 24.04 LTS 6.8.0-1046.52
  • linux-gkeop Ubuntu 24.04 LTS 6.8.0-1030.33
  • linux-raspi Ubuntu 24.04 LTS 6.8.0-1047.51

ubuntu advisories UBUNTU-CVE-2025-37879

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

  • dtb-aarch64 openSUSE Leap 15.6 6.4.0-150600.23.53.1
  • kernel-64kb SLE Module for Basesystem 15 SP6, openSUSE Leap 15.6 6.4.0-150600.23.53.1
  • kernel-syms SLE Module for Development Tools 15 SP6, openSUSE Leap 15.6 6.4.0-150600.23.53.1
  • kernel-obs-qa openSUSE Leap 15.6 6.4.0-150600.23.53.1
  • kernel-source SLE Module for Development Tools 15 SP6, SLE Module for Basesystem 15 SP6, openSUSE Leap 15.6 6.4.0-150600.23.53.1
  • kernel-default SLE Workstation Extension 15 SP6, SLE Module for Legacy 15 SP6, SLE Module for Basesystem 15 SP6 +3 more 6.4.0-150600.23.53.1
  • kernel-kvmsmall openSUSE Leap 15.6 6.4.0-150600.23.53.1
  • kernel-zfcpdump SLE Module for Basesystem 15 SP6, openSUSE Leap 15.6 6.4.0-150600.23.53.1

suse advisories SUSE-SU-2025:02000-1SUSE-SU-2025:01983-1SUSE-SU-2025:01972-1SUSE-SU-2025:20413-1SUSE-SU-2025:01967-1SUSE-SU-2025:01965-1

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-2025-37879 updated cvss 6.1

kernel: 9p/net: fix improper handling of bogus negative read/write replies

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    affected: no fix planned “Out of support scope”
  • 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

0.72% chance of exploitation in the next 30 days, higher than 54% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 7.1 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

Affected products

  • Linux Linux

Classification

Weakness
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.