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Fencer Vulns
medium 5.5

CVE-2025-39819 json

fs/smb: Fix inconsistent refcnt update

published 2025-09-16 13 mo ago modified 2026-11-05 3 d ago also EUVD-2025-29595

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 4%
public exploits
0
none known

Summary

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

fs/smb: Fix inconsistent refcnt update

A possible inconsistent update of refcount was identified in `smb2_compound_op`. Such inconsistent update could lead to possible resource leaks.

Why it is a possible bug: 1. In the comment section of the function, it clearly states that the reference to `cfile` should be dropped after calling this function. 2. Every control flow path would check and drop the reference to `cfile`, except the patched one. 3. Existing callers would not handle refcount update of `cfile` if -ENOMEM is returned.

To fix the bug, an extra goto label "out" is added, to make sure that the cleanup logic would always be respected. As the problem is caused by the allocation failure of `vars`, the cleanup logic between label "finished" and "out" can be safely ignored. According to the definition of function `is_replayable_error`, the error code of "-ENOMEM" is not recoverable. Therefore, the replay logic also gets ignored.

Patch / fix

  • Linux Linux 6.1.150, 6.6.104, 6.12.45, 6.16.5, 6.17
  • Siemens SIMATIC CN 4100 V5.0
  • linux Debian 12 6.1.153-1
  • linux Debian 13 6.12.48-1
  • linux Debian 14 6.16.5-1

debian advisories DEBIAN-CVE-2025-39819

  • linux Ubuntu 24.04 LTS 6.8.0-106.106
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1050.53
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1052.55
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1048.53
  • linux-ibm Ubuntu 24.04 LTS 6.8.0-1049.49
  • linux-azure Ubuntu 24.04 LTS 6.8.0-1051.57
  • linux-gkeop Ubuntu 24.04 LTS 6.8.0-1035.38
  • linux-raspi Ubuntu 24.04 LTS 6.8.0-1050.54

ubuntu advisories UBUNTU-CVE-2025-39819

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 5.14.0-570.58.1.el9_6
  • rv RHEL 9 5.14.0-570.58.1.el9_6
  • perf RHEL 9 5.14.0-570.58.1.el9_6
  • rtla RHEL 9 5.14.0-570.58.1.el9_6
  • libperf RHEL 9 5.14.0-570.58.1.el9_6
  • kernel-rt RHEL 9 5.14.0-570.58.1.el9_6
  • kernel-64k RHEL 9 5.14.0-570.58.1.el9_6
  • kernel-core RHEL 9 5.14.0-570.58.1.el9_6

red hat advisories RHSA-2025:19105

  • kernel-source Linux Micro 6.1, Linux Micro 6.0 6.4.0-38.1
  • kernel-default Linux Micro 6.1, Linux Micro 6.0 6.4.0-38.1
  • kernel-kvmsmall Linux Micro 6.1, Linux Micro 6.0 6.4.0-38.1
  • kernel-default-base Linux Micro 6.1, Linux Micro 6.0 6.4.0-38.1.21.15
  • kernel-rt Linux Micro 6.1, Linux Micro 6.0 6.4.0-39.1
  • kernel-source-rt Linux Micro 6.1, Linux Micro 6.0 6.4.0-39.1
  • kernel-rt Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.61.1
  • kernel-syms-rt Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.61.1

suse advisories SUSE-SU-2026:20473-1SUSE-SU-2026:20496-1SUSE-SU-2026:20039-1SUSE-SU-2026:20059-1SUSE-SU-2025:4521-1SUSE-SU-2025:4517-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.8.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.8.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.8.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.8.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.8.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.8.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.8.1
  • kernel-kvmsmall openSUSE Leap 16.0 6.12.0-160000.8.1

opensuse advisories openSUSE-SU-2025:20172-1

  • kernel Rocky Linux 9 5.14.0-570.58.1.el9_6

rocky linux advisories RLSA-2025:19105

  • kernel Azure Linux 3.0 6.6.104.2-1

azure linux advisories AZL-67377

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-2025-39819 updated cvss 5.5

kernel: Linux kernel: Denial of Service via resource leak in SMB2 compound operations

  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 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 Enterprise Linux 10 kernel
    affected: no fix available “Fix deferred”
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-570.58.1.el9_6, perf 5.14.0-570.58.1.el9_6, rtla 5.14.0-570.58.1.el9_6, python3-perf 5.14.0-570.58.1.el9_6, kernel-devel-matched 5.14.0-570.58.1.el9_6, kernel-64k-devel-matched 5.14.0-570.58.1.el9_6, +7 more Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-570.58.1.el9_6, kernel-64k 5.14.0-570.58.1.el9_6, kernel-core 5.14.0-570.58.1.el9_6, kernel-tools 5.14.0-570.58.1.el9_6, kernel-modules 5.14.0-570.58.1.el9_6, kernel-64k-core 5.14.0-570.58.1.el9_6, +27 more Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-570.58.1.el9_6, kernel-debuginfo-common-s390x 5.14.0-570.58.1.el9_6, kernel-debuginfo-common-x86_64 5.14.0-570.58.1.el9_6, kernel-debuginfo-common-aarch64 5.14.0-570.58.1.el9_6, kernel-debuginfo-common-ppc64le 5.14.0-570.58.1.el9_6 Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-570.58.1.el9_6, kernel-rt-64k 5.14.0-570.58.1.el9_6, kernel-rt-core 5.14.0-570.58.1.el9_6, kernel-rt-modules 5.14.0-570.58.1.el9_6, kernel-rt-64k-core 5.14.0-570.58.1.el9_6, kernel-rt-debug-core 5.14.0-570.58.1.el9_6, +14 more Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-570.58.1.el9_6, kernel-rt-kvm 5.14.0-570.58.1.el9_6, kernel-rt-core 5.14.0-570.58.1.el9_6, kernel-rt-modules 5.14.0-570.58.1.el9_6, kernel-rt-debug-kvm 5.14.0-570.58.1.el9_6, kernel-rt-debug-core 5.14.0-570.58.1.el9_6, +6 more
    fixed: vendor fix RHSA-2025:19105
  • 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

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3 d ago

Exploit prediction

0.15% chance of exploitation in the next 30 days, higher than 4% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux
  • Siemens SIMATIC CN 4100

Classification

Technology feeds

References

Sources

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