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Fencer Vulns
high 7.1

CVE-2026-64298 json

NFSv4: include MAY_WRITE in open permission mask for O_TRUNC

published 2026-07-25 3 mo ago modified 2026-10-19 20 d ago also EUVD-2026-49010

cvss
7.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 3%
public exploits
0
none known

Summary

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

NFSv4: include MAY_WRITE in open permission mask for O_TRUNC

POSIX requires write permission to truncate a file, so an open() that specifies O_TRUNC must be authorized for write access regardless of the O_ACCMODE access mode.

nfs_open_permission_mask() builds the access mask passed to nfs_may_open(), which is the local authorization gate for OPENs the client serves itself from a cached write delegation via the can_open_delegated() path in nfs4_try_open_cached(). The mask is derived from O_ACCMODE alone, so an open(O_RDONLY | O_TRUNC) against a file the caller cannot write requests only MAY_READ and passes the local check. The OPEN is then satisfied locally and the truncation is issued to the server as a SETATTR(size=0) over the delegation stateid, which the server accepts under standard write-delegation semantics. POSIX requires that this open fail with EACCES.

Include MAY_WRITE in the mask whenever O_TRUNC is set so the local check matches the access the server would have enforced.

Patch / fix

  • Linux Linux 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.96, 6.18.39, 7.1.4, 7.2
  • linux Debian 12 6.1.180-1
  • linux Debian 13 6.12.96-1
  • linux Debian 14 7.1.4-1
  • linux-6.12 Debian 12 6.12.100-1~deb12u1

debian advisories DEBIAN-CVE-2026-64298

  • linux Ubuntu 22.04 LTS 5.15.0-198.208
  • linux Ubuntu 24.04 LTS 6.8.0-147.147
  • linux Ubuntu 26.04 LTS 7.0.0-31.31
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1117.124
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1067.70
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1012.12
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1118.128
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1071.79

ubuntu advisories UBUNTU-CVE-2026-64298

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 9 5.14.0-687.44.1.el9_8
  • rv RHEL 9 5.14.0-687.44.1.el9_8
  • perf RHEL 9 5.14.0-687.44.1.el9_8
  • rtla RHEL 9 5.14.0-687.44.1.el9_8
  • libperf RHEL 9 5.14.0-687.44.1.el9_8
  • kernel-rt RHEL 9 5.14.0-687.44.1.el9_8
  • kernel-64k RHEL 9 5.14.0-687.44.1.el9_8
  • kernel-core RHEL 9 5.14.0-687.44.1.el9_8

red hat advisories RHSA-2026:63129RHSA-2026:63014RHSA-2026:63013RHSA-2026:61887

  • kernel-rt Linux Micro 6.2 6.12.0-160000.38.1
  • kernel-64kb SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.38.1
  • kernel-source SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.38.1
  • kernel-default SLES 16.0, SLE High Availability Extension 16.0, Linux Micro 6.2 +1 more 6.12.0-160000.38.1
  • kernel-default-base SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.38.1.160000.2.23
  • kernel-syms SLES 16.0, Linux Micro Extras 6.2, SLES for SAP applications 16.0 6.12.0-160000.38.1
  • kernel-azure SLES for SAP applications 16.0, SLES 16.0 6.12.0-160000.38.1
  • kernel-obs-qa SLES for SAP applications 16.0, SLES 16.0 6.12.0-160000.38.1

suse advisories SUSE-SU-2026:23887-1SUSE-SU-2026:23902-1SUSE-SU-2026:23897-1SUSE-SU-2026:23881-1SUSE-SU-2026:3810-1SUSE-SU-2026:3790-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.38.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.38.1

opensuse advisories openSUSE-SU-2026:21910-1openSUSE-SU-2026:11476-1

  • kernel-rt AlmaLinux 8 4.18.0-553.159.1.rt7.500.el8_10
  • kernel-rt-core AlmaLinux 8 4.18.0-553.159.1.rt7.500.el8_10
  • kernel-rt-modules AlmaLinux 8 4.18.0-553.159.1.rt7.500.el8_10
  • kernel-rt-debug-core AlmaLinux 8 4.18.0-553.159.1.rt7.500.el8_10
  • kernel-rt-debug-modules AlmaLinux 8 4.18.0-553.159.1.rt7.500.el8_10
  • kernel-rt-modules-extra AlmaLinux 8 4.18.0-553.159.1.rt7.500.el8_10
  • kernel-rt-debug-modules-extra AlmaLinux 8 4.18.0-553.159.1.rt7.500.el8_10
  • kernel AlmaLinux 8 4.18.0-553.159.1.el8_10

almalinux advisories ALSA-2026:63013ALSA-2026:63014ALSA-2026:63129ALSA-2026:61887

  • kernel Rocky Linux 9 5.14.0-687.44.1.el9_8
  • kernel-rt Rocky Linux 8 4.18.0-553.159.1.rt7.500.el8_10
  • kernel Rocky Linux 8 4.18.0-553.159.1.el8_10
  • kernel Rocky Linux 10 6.12.0-211.50.1.el10_2

rocky linux advisories RLSA-2026:63129RLSA-2026:63013RLSA-2026:63014RLSA-2026:61887

  • kernel Azure Linux 3.0 6.6.145.2-1

azure linux advisories AZL-93668

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-2026-64298 updated cvss 7.0

kernel: NFSv4: include MAY_WRITE in open permission mask for O_TRUNC

  • 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 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more
    affected: no fix available
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.44.1.el9_8, perf 5.14.0-687.44.1.el9_8, rtla 5.14.0-687.44.1.el9_8, python3-perf 5.14.0-687.44.1.el9_8, kernel-devel-matched 5.14.0-687.44.1.el9_8, kernel-64k-devel-matched 5.14.0-687.44.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:63129
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.50.1.el10_2, perf 6.12.0-211.50.1.el10_2, rtla 6.12.0-211.50.1.el10_2, python3-perf 6.12.0-211.50.1.el10_2, kernel-devel-matched 6.12.0-211.50.1.el10_2, kernel-64k-devel-matched 6.12.0-211.50.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-553.159.1.el8_10, kernel 4.18.0-553.159.1.el8_10, bpftool 4.18.0-553.159.1.el8_10, kernel-core 4.18.0-553.159.1.el8_10, kernel-tools 4.18.0-553.159.1.el8_10, python3-perf 4.18.0-553.159.1.el8_10, +15 more
    fixed: vendor fix RHSA-2026:63014
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.44.1.el9_8, kernel-64k 5.14.0-687.44.1.el9_8, kernel-core 5.14.0-687.44.1.el9_8, kernel-tools 5.14.0-687.44.1.el9_8, kernel-modules 5.14.0-687.44.1.el9_8, kernel-64k-core 5.14.0-687.44.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:63129
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.50.1.el10_2, kernel-64k 6.12.0-211.50.1.el10_2, kernel-core 6.12.0-211.50.1.el10_2, kernel-tools 6.12.0-211.50.1.el10_2, kernel-modules 6.12.0-211.50.1.el10_2, kernel-64k-core 6.12.0-211.50.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.44.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.44.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.44.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.44.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.44.1.el9_8
    fixed: vendor fix RHSA-2026:63129
show 8 more
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.50.1.el10_2
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-553.159.1.el8_10, kernel-debuginfo-common-aarch64 4.18.0-553.159.1.el8_10, kernel-debuginfo-common-ppc64le 4.18.0-553.159.1.el8_10
    fixed: vendor fix RHSA-2026:63014
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-553.159.1.rt7.500.el8_10, kernel-rt-kvm 4.18.0-553.159.1.rt7.500.el8_10, kernel-rt-core 4.18.0-553.159.1.rt7.500.el8_10, kernel-rt-modules 4.18.0-553.159.1.rt7.500.el8_10, kernel-rt-debug-kvm 4.18.0-553.159.1.rt7.500.el8_10, kernel-rt-debug-core 4.18.0-553.159.1.rt7.500.el8_10, +4 more
    fixed: vendor fix RHSA-2026:63013
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.44.1.el9_8, kernel-rt-64k 5.14.0-687.44.1.el9_8, kernel-rt-core 5.14.0-687.44.1.el9_8, kernel-rt-modules 5.14.0-687.44.1.el9_8, kernel-rt-64k-core 5.14.0-687.44.1.el9_8, kernel-rt-debug-core 5.14.0-687.44.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:63129
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.50.1.el10_2, kernel-rt-64k 6.12.0-211.50.1.el10_2, kernel-rt-core 6.12.0-211.50.1.el10_2, kernel-rt-modules 6.12.0-211.50.1.el10_2, kernel-rt-64k-core 6.12.0-211.50.1.el10_2, kernel-rt-debug-core 6.12.0-211.50.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.44.1.el9_8, kernel-rt-core 5.14.0-687.44.1.el9_8, kernel-rt-modules 5.14.0-687.44.1.el9_8, kernel-rt-debug-core 5.14.0-687.44.1.el9_8, kernel-rt-modules-core 5.14.0-687.44.1.el9_8, kernel-rt-debug-modules 5.14.0-687.44.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:63129
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.50.1.el10_2, kernel-rt-core 6.12.0-211.50.1.el10_2, kernel-rt-modules 6.12.0-211.50.1.el10_2, kernel-rt-debug-core 6.12.0-211.50.1.el10_2, kernel-rt-modules-core 6.12.0-211.50.1.el10_2, kernel-rt-debug-modules 6.12.0-211.50.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-553.159.1.rt7.500.el8_10, kernel-rt-core 4.18.0-553.159.1.rt7.500.el8_10, kernel-rt-modules 4.18.0-553.159.1.rt7.500.el8_10, kernel-rt-debug-core 4.18.0-553.159.1.rt7.500.el8_10, kernel-rt-debug-modules 4.18.0-553.159.1.rt7.500.el8_10, kernel-rt-modules-extra 4.18.0-553.159.1.rt7.500.el8_10, +2 more
    fixed: vendor fix RHSA-2026:63013

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

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
24 d ago

Exploit prediction

0.15% chance of exploitation in the next 30 days, higher than 3% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

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