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Fencer Vulns
critical 9.8

CVE-2026-90036 in the critical feed json

NFSD: Prevent client use-after-free during blocked-lock reaping

published 2026-09-16 54 d ago modified 2026-10-21 19 d ago also EUVD-2026-80644

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 41%
public exploits
0
none known

Summary

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

NFSD: Prevent client use-after-free during blocked-lock reaping

A bare lock owner -- its only remaining reference a blocked lock on nn->blocked_locks_lru -- holds a raw pointer to its nfs4_client but no reference keeping the client alive. When the per-net laundromat reaps such a lock, freeing the nbl drops the owner reference held through flc_owner, and the final nfs4_put_stateowner() takes the client's cl_lock. Because the laundromat detaches the nbl first, __destroy_client() no longer finds it, so a concurrent force_expire_client() can free the client before nfs4_put_stateowner() runs, dereferencing cl_lock in freed memory.

Pin the client with cl_rpc_users before dropping nn->blocked_locks_lock, and skip clients already expiring, whose blocked locks __destroy_client() frees while holding an owner reference. Take nn->client_lock outside nn->blocked_locks_lock. Every other site holds nn->blocked_locks_lock as a leaf, acquiring no further lock, so placing nn->client_lock outside it cannot form a lock-order cycle.

Patch / fix

  • Linux Linux 6.6.160, 6.12.111, 6.18.51, 7.2.5, 7.3
  • linux Debian 13 6.12.111-1
  • linux Debian 14 7.2.6-1
  • linux-6.12 Debian 12 6.12.111-1~deb12u1

debian advisories DEBIAN-CVE-2026-90036

  • linux Ubuntu 26.04 LTS 7.0.0-42.42
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1016.17
  • linux-gcp Ubuntu 26.04 LTS 7.0.0-1016.18
  • linux-ibm Ubuntu 26.04 LTS 7.0.0-1017.17
  • linux-riscv Ubuntu 26.04 LTS 7.0.0-42.42.1
  • linux-oracle Ubuntu 26.04 LTS 7.0.0-1015.16
  • linux-hwe-7.0 Ubuntu 24.04 LTS 7.0.0-42.42~24.04.1
  • linux-oem-7.0 Ubuntu 26.04 LTS 7.0.0-1017.17

ubuntu advisories UBUNTU-CVE-2026-90036

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 RHEL 10.2 6.12.0-211.66.1.el10_2
  • rv RHEL 10.2 6.12.0-211.66.1.el10_2
  • perf RHEL 10.2 6.12.0-211.66.1.el10_2
  • rtla RHEL 10.2 6.12.0-211.66.1.el10_2
  • libperf RHEL 10.2 6.12.0-211.66.1.el10_2
  • kernel-rt RHEL 10.2 6.12.0-211.66.1.el10_2
  • kernel-64k RHEL 10.2 6.12.0-211.66.1.el10_2
  • kernel-core RHEL 10.2 6.12.0-211.66.1.el10_2

red hat advisories RHSA-2026:83207RHSA-2026:83157RHSA-2026:83159RHSA-2026:83156

  • kernel-source openSUSE Tumbleweed 7.2.7-1.1

opensuse advisories openSUSE-SU-2026:11880-1

  • kernel AlmaLinux 9 5.14.0-687.58.1.el9_8
  • rv AlmaLinux 9 5.14.0-687.58.1.el9_8
  • perf AlmaLinux 9 5.14.0-687.58.1.el9_8
  • rtla AlmaLinux 9 5.14.0-687.58.1.el9_8
  • libperf AlmaLinux 9 5.14.0-687.58.1.el9_8
  • kernel-rt AlmaLinux 9 5.14.0-687.58.1.el9_8
  • kernel-64k AlmaLinux 9 5.14.0-687.58.1.el9_8
  • kernel-core AlmaLinux 9 5.14.0-687.58.1.el9_8

almalinux advisories ALSA-2026:83156ALSA-2026:83157ALSA-2026:83159ALSA-2026:83207

  • kernel Rocky Linux 10 6.12.0-211.66.1.el10_2
  • kernel Rocky Linux 9 5.14.0-687.58.1.el9_8
  • kernel-rt Rocky Linux 8 4.18.0-553.174.1.rt7.515.el8_10
  • kernel Rocky Linux 8 4.18.0-553.174.1.el8_10

rocky linux advisories RLSA-2026:83207RLSA-2026:83156RLSA-2026:83159RLSA-2026:83157

  • kernel Azure Linux 3.0 6.6.161.1-1

azure linux advisories AZL-101540

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2026-90036 updated cvss 8.8

kernel: NFSD: Prevent client use-after-free during blocked-lock reaping

  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: workaround, no fix available
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    under investigation
  • Red Hat Enterprise Linux kernel-modules-internal 6.12.0-211.66.1.el10_2
    fixed: vendor fix RHSA-2026:83207
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.58.1.el9_8, perf 5.14.0-687.58.1.el9_8, rtla 5.14.0-687.58.1.el9_8, python3-perf 5.14.0-687.58.1.el9_8, kernel-devel-matched 5.14.0-687.58.1.el9_8, kernel-64k-devel-matched 5.14.0-687.58.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:83156
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.66.1.el10_2, perf 6.12.0-211.66.1.el10_2, rtla 6.12.0-211.66.1.el10_2, python3-perf 6.12.0-211.66.1.el10_2, kernel-devel-matched 6.12.0-211.66.1.el10_2, kernel-64k-devel-matched 6.12.0-211.66.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:83207
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-553.174.1.el8_10, kernel 4.18.0-553.174.1.el8_10, bpftool 4.18.0-553.174.1.el8_10, kernel-core 4.18.0-553.174.1.el8_10, kernel-tools 4.18.0-553.174.1.el8_10, python3-perf 4.18.0-553.174.1.el8_10, +15 more
    fixed: vendor fix RHSA-2026:83157
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.58.1.el9_8, kernel-64k 5.14.0-687.58.1.el9_8, kernel-core 5.14.0-687.58.1.el9_8, kernel-tools 5.14.0-687.58.1.el9_8, kernel-modules 5.14.0-687.58.1.el9_8, kernel-64k-core 5.14.0-687.58.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:83156
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.66.1.el10_2, kernel-64k 6.12.0-211.66.1.el10_2, kernel-core 6.12.0-211.66.1.el10_2, kernel-tools 6.12.0-211.66.1.el10_2, kernel-modules 6.12.0-211.66.1.el10_2, kernel-64k-core 6.12.0-211.66.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:83207
show 11 more
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.58.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.58.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.58.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.58.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.58.1.el9_8
    fixed: vendor fix RHSA-2026:83156
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.66.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.66.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.66.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.66.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.66.1.el10_2
    fixed: vendor fix RHSA-2026:83207
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-553.174.1.el8_10, kernel-debuginfo-common-aarch64 4.18.0-553.174.1.el8_10, kernel-debuginfo-common-ppc64le 4.18.0-553.174.1.el8_10
    fixed: vendor fix RHSA-2026:83157
  • Red Hat Enterprise Linux Hidden (v. 10) kernel-modules-internal 6.12.0-211.66.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.66.1.el10_2
    fixed: vendor fix RHSA-2026:83207
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-553.174.1.rt7.515.el8_10, kernel-rt-kvm 4.18.0-553.174.1.rt7.515.el8_10, kernel-rt-core 4.18.0-553.174.1.rt7.515.el8_10, kernel-rt-modules 4.18.0-553.174.1.rt7.515.el8_10, kernel-rt-debug-kvm 4.18.0-553.174.1.rt7.515.el8_10, kernel-rt-debug-core 4.18.0-553.174.1.rt7.515.el8_10, +4 more
    fixed: vendor fix RHSA-2026:83159
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.58.1.el9_8, kernel-rt-64k 5.14.0-687.58.1.el9_8, kernel-rt-core 5.14.0-687.58.1.el9_8, kernel-rt-modules 5.14.0-687.58.1.el9_8, kernel-rt-64k-core 5.14.0-687.58.1.el9_8, kernel-rt-debug-core 5.14.0-687.58.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:83156
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.66.1.el10_2, kernel-rt-64k 6.12.0-211.66.1.el10_2, kernel-rt-core 6.12.0-211.66.1.el10_2, kernel-rt-modules 6.12.0-211.66.1.el10_2, kernel-rt-64k-core 6.12.0-211.66.1.el10_2, kernel-rt-debug-core 6.12.0-211.66.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:83207
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.58.1.el9_8, kernel-rt-core 5.14.0-687.58.1.el9_8, kernel-rt-modules 5.14.0-687.58.1.el9_8, kernel-rt-debug-core 5.14.0-687.58.1.el9_8, kernel-rt-modules-core 5.14.0-687.58.1.el9_8, kernel-rt-debug-modules 5.14.0-687.58.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:83156
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.66.1.el10_2, kernel-rt-core 6.12.0-211.66.1.el10_2, kernel-rt-modules 6.12.0-211.66.1.el10_2, kernel-rt-debug-core 6.12.0-211.66.1.el10_2, kernel-rt-modules-core 6.12.0-211.66.1.el10_2, kernel-rt-debug-modules 6.12.0-211.66.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:83207
  • Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-553.174.1.rt7.515.el8_10, kernel-rt-core 4.18.0-553.174.1.rt7.515.el8_10, kernel-rt-modules 4.18.0-553.174.1.rt7.515.el8_10, kernel-rt-debug-core 4.18.0-553.174.1.rt7.515.el8_10, kernel-rt-debug-modules 4.18.0-553.174.1.rt7.515.el8_10, kernel-rt-modules-extra 4.18.0-553.174.1.rt7.515.el8_10, +2 more
    fixed: vendor fix RHSA-2026:83159
  • Red Hat OpenShift Container Platform 4.22 rhcos 4.22.9.8.202610241758
    fixed: vendor fix RHSA-2026:89197

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

0.48% chance of exploitation in the next 30 days, higher than 41% 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

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.