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Fencer Vulns
high 8.1

CVE-2026-93787 json

smb: client: bound dirent name against end of SMB response in cifs_filldir

published 2026-09-24 45 d ago modified 2026-10-03 37 d ago also EUVD-2026-86174

cvss
8.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 28%
public exploits
0
none known

Summary

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

smb: client: bound dirent name against end of SMB response in cifs_filldir

cifs_filldir() copies the entry name out of an SMB1 TRANS2_FIND_FIRST / FIND_NEXT response using a length (de.namelen) supplied by the server. The kmalloc'd SMB response buffer is bounded, but nothing checks that de.name + de.namelen still lies inside that buffer before the eventual filldir64() -> verify_dirent_name() -> memchr() reads namelen bytes.

A hostile SMB1 server that returns an oversized FileNameLength in a directory entry therefore causes memchr() to read past the end of the response slab buffer. Reachable from any user who can list a directory on a CIFS mount served by an attacker-controlled server (getdents64() on the mounted directory):

BUG: KASAN: slab-out-of-bounds in memchr+0x71/0x80 Read of size 1 at addr ffff88800e0640cc by task poc/115 Call Trace: dump_stack_lvl+0x64/0x80 print_report+0xce/0x620 kasan_report+0xec/0x120 memchr+0x71/0x80 filldir64+0x4c/0x6a0 cifs_filldir.constprop.0+0x9bb/0x1e00 cifs_readdir+0x2101/0x3380 iterate_dir+0x19c/0x520 __x64_sys_getdents64+0x126/0x210 do_syscall_64+0x107/0x5a0 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Pass the end-of-response pointer down to cifs_filldir() and reject entries whose name would extend past that boundary.

This bug was discovered by Artiphishell's vTriage pipeline, which generated a userspace reproducer (an emulated hostile SMB1 server plus a getdents64() client) that reliably triggers the KASAN report on an unpatched kernel. The fix below was drafted with the Claude coding assistant; a userspace reproducer is available on request.

Patch / fix

  • Linux Linux 6.1.189, 6.6.158, 6.12.111, 6.18.53, 7.2
  • linux Debian 12 6.1.190-1
  • 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-2026-93787

  • 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-2026-93787

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-rt Real Time Module 15 SP7 6.4.0-150700.7.81.1
  • kernel-syms-rt Real Time Module 15 SP7 6.4.0-150700.7.81.1
  • kernel-source-rt Real Time Module 15 SP7 6.4.0-150700.7.81.1
  • kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.87.3
  • kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.87.1
  • kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.87.3
  • kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.87.3
  • kernel-default SLE Workstation Extension 15 SP7, SLE Module for Legacy 15 SP7, SLE Module for Basesystem 15 SP7 +2 more 6.4.0-150700.53.87.3

suse advisories SUSE-SU-2026:5121-1SUSE-SU-2026:4940-1SUSE-SU-2026:4935-1SUSE-SU-2026:4934-1SUSE-SU-2026:24473-1SUSE-SU-2026:24553-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.40.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.40.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.40.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.40.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.40.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.40.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.40.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.40.1

opensuse advisories openSUSE-SU-2026:22167-1

  • kernel AlmaLinux 8 4.18.0-553.181.1.el8_10
  • perf AlmaLinux 8 4.18.0-553.181.1.el8_10
  • bpftool AlmaLinux 8 4.18.0-553.181.1.el8_10
  • kernel-core AlmaLinux 8 4.18.0-553.181.1.el8_10
  • kernel-tools AlmaLinux 8 4.18.0-553.181.1.el8_10
  • python3-perf AlmaLinux 8 4.18.0-553.181.1.el8_10
  • kernel-modules AlmaLinux 8 4.18.0-553.181.1.el8_10
  • kernel-zfcpdump AlmaLinux 8 4.18.0-553.181.1.el8_10

almalinux advisories ALSA-2026:93436ALSA-2026:93437

  • kernel Rocky Linux 10 6.12.0-211.72.1.el10_2
  • kernel Rocky Linux 9 5.14.0-687.64.1.el9_8

rocky linux advisories RLSA-2026:93413RLSA-2026:93412

  • kernel Azure Linux 3.0 6.6.158.1-1

azure linux advisories AZL-103571

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-2026-93787 updated cvss 8.1

kernel: smb: client: bound dirent name against end of SMB response in cifs_filldir

  • 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 kernel-modules-internal 6.12.0-211.72.1.el10_2
    fixed: vendor fix RHSA-2026:93413
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.64.1.el9_8, perf 5.14.0-687.64.1.el9_8, rtla 5.14.0-687.64.1.el9_8, python3-perf 5.14.0-687.64.1.el9_8, kernel-devel-matched 5.14.0-687.64.1.el9_8, kernel-64k-devel-matched 5.14.0-687.64.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:93412
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.72.1.el10_2, perf 6.12.0-211.72.1.el10_2, rtla 6.12.0-211.72.1.el10_2, python3-perf 6.12.0-211.72.1.el10_2, kernel-devel-matched 6.12.0-211.72.1.el10_2, kernel-64k-devel-matched 6.12.0-211.72.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:93413
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-553.181.1.el8_10, kernel 4.18.0-553.181.1.el8_10, bpftool 4.18.0-553.181.1.el8_10, kernel-core 4.18.0-553.181.1.el8_10, kernel-tools 4.18.0-553.181.1.el8_10, python3-perf 4.18.0-553.181.1.el8_10, +15 more
    fixed: vendor fix RHSA-2026:93436
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.64.1.el9_8, kernel-64k 5.14.0-687.64.1.el9_8, kernel-core 5.14.0-687.64.1.el9_8, kernel-tools 5.14.0-687.64.1.el9_8, kernel-modules 5.14.0-687.64.1.el9_8, kernel-64k-core 5.14.0-687.64.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:93412
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.72.1.el10_2, kernel-64k 6.12.0-211.72.1.el10_2, kernel-core 6.12.0-211.72.1.el10_2, kernel-tools 6.12.0-211.72.1.el10_2, kernel-modules 6.12.0-211.72.1.el10_2, kernel-64k-core 6.12.0-211.72.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:93413
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.64.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.64.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.64.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.64.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.64.1.el9_8
    fixed: vendor fix RHSA-2026:93412
show 10 more
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.72.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.72.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.72.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.72.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.72.1.el10_2
    fixed: vendor fix RHSA-2026:93413
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-553.181.1.el8_10, kernel-debuginfo-common-aarch64 4.18.0-553.181.1.el8_10, kernel-debuginfo-common-ppc64le 4.18.0-553.181.1.el8_10
    fixed: vendor fix RHSA-2026:93436
  • Red Hat Enterprise Linux Hidden (v. 10) kernel-modules-internal 6.12.0-211.72.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.72.1.el10_2
    fixed: vendor fix RHSA-2026:93413
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-553.181.1.rt7.522.el8_10, kernel-rt-kvm 4.18.0-553.181.1.rt7.522.el8_10, kernel-rt-core 4.18.0-553.181.1.rt7.522.el8_10, kernel-rt-modules 4.18.0-553.181.1.rt7.522.el8_10, kernel-rt-debug-kvm 4.18.0-553.181.1.rt7.522.el8_10, kernel-rt-debug-core 4.18.0-553.181.1.rt7.522.el8_10, +4 more
    fixed: vendor fix RHSA-2026:93437
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.64.1.el9_8, kernel-rt-64k 5.14.0-687.64.1.el9_8, kernel-rt-core 5.14.0-687.64.1.el9_8, kernel-rt-modules 5.14.0-687.64.1.el9_8, kernel-rt-64k-core 5.14.0-687.64.1.el9_8, kernel-rt-debug-core 5.14.0-687.64.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:93412
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.72.1.el10_2, kernel-rt-64k 6.12.0-211.72.1.el10_2, kernel-rt-core 6.12.0-211.72.1.el10_2, kernel-rt-modules 6.12.0-211.72.1.el10_2, kernel-rt-64k-core 6.12.0-211.72.1.el10_2, kernel-rt-debug-core 6.12.0-211.72.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:93413
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.64.1.el9_8, kernel-rt-core 5.14.0-687.64.1.el9_8, kernel-rt-modules 5.14.0-687.64.1.el9_8, kernel-rt-debug-core 5.14.0-687.64.1.el9_8, kernel-rt-modules-core 5.14.0-687.64.1.el9_8, kernel-rt-debug-modules 5.14.0-687.64.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:93412
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.72.1.el10_2, kernel-rt-core 6.12.0-211.72.1.el10_2, kernel-rt-modules 6.12.0-211.72.1.el10_2, kernel-rt-debug-core 6.12.0-211.72.1.el10_2, kernel-rt-modules-core 6.12.0-211.72.1.el10_2, kernel-rt-debug-modules 6.12.0-211.72.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:93413
  • Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-553.181.1.rt7.522.el8_10, kernel-rt-core 4.18.0-553.181.1.rt7.522.el8_10, kernel-rt-modules 4.18.0-553.181.1.rt7.522.el8_10, kernel-rt-debug-core 4.18.0-553.181.1.rt7.522.el8_10, kernel-rt-debug-modules 4.18.0-553.181.1.rt7.522.el8_10, kernel-rt-modules-extra 4.18.0-553.181.1.rt7.522.el8_10, +2 more
    fixed: vendor fix RHSA-2026:93437
  • 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
    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

0.34% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/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.