CVE-2025-40285: smb/server: fix possible refcount leak in smb2_sess_setup()

Q: What is the severity of CVE-2025-40285?

CVE-2025-40285 has a medium severity level due to the potential for a reference count leak in session handling.

Q: How do I fix CVE-2025-40285?

To fix CVE-2025-40285, update your Linux kernel to the latest stable version where the vulnerability has been resolved.

Q: What impact does CVE-2025-40285 have on my system?

CVE-2025-40285 can lead to resource leaks, which may ultimately affect system stability and performance.

Q: Is CVE-2025-40285 exploitable remotely?

CVE-2025-40285 is not classified as a remote exploit, as it pertains to session management within the kernel.

Q: When was CVE-2025-40285 discovered?

CVE-2025-40285 was identified and documented as part of vulnerabilities addressed in the Linux kernel.

Published Dec 6, 2025

Updated

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

smb/server: fix possible refcount leak in smb2sesssetup()

Reference count of ksmbdsession will leak when session need reconnect. Fix this by adding the missing ksmbdusersessionput().

Affected Software

183 affected componentsFixes available

Linux Linux kernel

ubuntu/linux-hwe-edge*

ubuntu/linux-aws-5.0*

ubuntu/linux-aws-5.3*

ubuntu/linux-azure*

ubuntu/linux-azure-5.3*

ubuntu/linux-azure-edge*

ubuntu/linux-gcp*

ubuntu/linux-gcp-5.3*

ubuntu/linux-gke-4.15*

ubuntu/linux-gke-5.4*

ubuntu/linux-gkeop-5.4*

ubuntu/linux-hwe*

ubuntu/linux-hwe-edge*

ubuntu/linux-oem*

ubuntu/linux-oracle-5.0*

ubuntu/linux-oracle-5.3*

ubuntu/linux-aws-5.11*

ubuntu/linux-aws-5.13*

ubuntu/linux-aws-5.15*

ubuntu/linux-aws-5.8*

ubuntu/linux-azure-5.11*

ubuntu/linux-azure-5.13*

ubuntu/linux-azure-5.15*

ubuntu/linux-azure-5.8*

ubuntu/linux-azure-fde*

ubuntu/linux-azure-fde-5.15*

ubuntu/linux-gcp-5.11*

ubuntu/linux-gcp-5.13*

ubuntu/linux-gcp-5.15*

ubuntu/linux-gcp-5.8*

ubuntu/linux-gke*

ubuntu/linux-gke-5.15*

ubuntu/linux-gkeop*

ubuntu/linux-gkeop-5.15*

ubuntu/linux-hwe-5.11*

ubuntu/linux-hwe-5.13*

ubuntu/linux-hwe-5.15*

ubuntu/linux-hwe-5.8*

ubuntu/linux-ibm-5.15*

ubuntu/linux-intel-5.13*

ubuntu/linux-intel-iotg-5.15*

ubuntu/linux-lowlatency-hwe-5.15*

ubuntu/linux-nvidia-tegra-5.15*

ubuntu/linux-oem-5.10*

ubuntu/linux-oem-5.13*

ubuntu/linux-oem-5.6*

ubuntu/linux-oracle-5.11*

ubuntu/linux-oracle-5.13*

ubuntu/linux-oracle-5.15*

ubuntu/linux-oracle-5.8*

ubuntu/linux-raspi2*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.11*

ubuntu/linux-riscv-5.15*

ubuntu/linux-riscv-5.8*

ubuntu/linux*

ubuntu/linux-allwinner-5.19*

ubuntu/linux-aws*

ubuntu/linux-aws-5.19*

ubuntu/linux-aws-6.2*

ubuntu/linux-aws-6.5*

ubuntu/linux-aws-6.8<6.8.0-1050.53~22.04.1

6.8.0-1050.53~22.04.1

ubuntu/linux-azure*

ubuntu/linux-azure-5.19*

ubuntu/linux-azure-6.2*

ubuntu/linux-azure-6.5*

ubuntu/linux-azure-6.8<6.8.0-1051.57~22.04.1

6.8.0-1051.57~22.04.1

ubuntu/linux-azure-fde*

ubuntu/linux-azure-fde-5.19*

ubuntu/linux-azure-fde-6.2*

ubuntu/linux-azure-fde-6.8<6.8.0-1058.65~22.04.1

6.8.0-1058.65~22.04.1

ubuntu/linux-gcp*

ubuntu/linux-gcp-5.19*

ubuntu/linux-gcp-6.2*

ubuntu/linux-gcp-6.5*

ubuntu/linux-gcp-6.8<6.8.0-1052.55~22.04.1

6.8.0-1052.55~22.04.1

ubuntu/linux-gke*

ubuntu/linux-gkeop*

ubuntu/linux-hwe-5.19*

ubuntu/linux-hwe-6.2*

ubuntu/linux-hwe-6.5*

ubuntu/linux-hwe-6.8<6.8.0-106.106~22.04.1

6.8.0-106.106~22.04.1

ubuntu/linux-ibm*

ubuntu/linux-ibm-6.8<6.8.0-1049.49~22.04.1

6.8.0-1049.49~22.04.1

ubuntu/linux-intel-iot-realtime*

ubuntu/linux-intel-iotg*

ubuntu/linux-kvm*

ubuntu/linux-lowlatency*

ubuntu/linux-lowlatency-hwe-5.19*

ubuntu/linux-lowlatency-hwe-6.2*

ubuntu/linux-lowlatency-hwe-6.5*

ubuntu/linux-lowlatency-hwe-6.8<6.8.0-106.106.1~22.04.1

6.8.0-106.106.1~22.04.1

ubuntu/linux-nvidia*

ubuntu/linux-nvidia-6.2*

ubuntu/linux-nvidia-6.5*

ubuntu/linux-nvidia-6.8<6.8.0-1049.52~22.04.1

6.8.0-1049.52~22.04.1

ubuntu/linux-nvidia-tegra*

ubuntu/linux-nvidia-tegra-igx*

ubuntu/linux-oem-5.17*

ubuntu/linux-oem-6.0*

ubuntu/linux-oem-6.1*

ubuntu/linux-oem-6.5*

ubuntu/linux-oracle*

ubuntu/linux-oracle-6.5*

ubuntu/linux-oracle-6.8<6.8.0-1047.48~22.04.1

6.8.0-1047.48~22.04.1

ubuntu/linux-raspi*

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.19*

ubuntu/linux-riscv-6.5*

ubuntu/linux-riscv-6.8<6.8.0-106.106~22.04.1

6.8.0-106.106~22.04.1

ubuntu/linux-starfive-5.19*

ubuntu/linux-starfive-6.2*

ubuntu/linux-starfive-6.5*

ubuntu/linux-xilinx-zynqmp*

ubuntu/linux-bluefield*

ubuntu/linux-intel-iot-realtime*

ubuntu/linux-realtime*

ubuntu/linux-realtime-6.8<6.8.1-1045.46~22.04.1

6.8.1-1045.46~22.04.1

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux<6.8.0-106.106

6.8.0-106.106

ubuntu/linux-aws<6.8.0-1050.53

6.8.0-1050.53

ubuntu/linux-aws-6.14*

ubuntu/linux-aws-6.17<6.17.0-1007.7~24.04.1

6.17.0-1007.7~24.04.1

ubuntu/linux-azure<6.8.0-1051.57

6.8.0-1051.57

ubuntu/linux-azure-6.11*

ubuntu/linux-azure-6.14*

ubuntu/linux-azure-fde<6.8.0-1058.65

6.8.0-1058.65

ubuntu/linux-azure-fde-6.14*

ubuntu/linux-azure-nvidia<6.8.0-1039.42

6.8.0-1039.42

ubuntu/linux-azure-nvidia-6.14*

ubuntu/linux-gcp<6.8.0-1052.55

6.8.0-1052.55

ubuntu/linux-gcp-6.11*

ubuntu/linux-gcp-6.14*

ubuntu/linux-gcp-6.17<6.17.0-1008.8~24.04.1

6.17.0-1008.8~24.04.1

ubuntu/linux-gke<6.8.0-1048.53

6.8.0-1048.53

ubuntu/linux-gkeop<6.8.0-1035.38

6.8.0-1035.38

ubuntu/linux-hwe-6.11*

ubuntu/linux-hwe-6.14*

ubuntu/linux-ibm<6.8.0-1049.49

6.8.0-1049.49

ubuntu/linux-lowlatency<6.8.0-106.106.1

6.8.0-106.106.1

ubuntu/linux-lowlatency-hwe-6.11*

ubuntu/linux-nvidia<6.8.0-1049.52

6.8.0-1049.52

ubuntu/linux-nvidia-6.11*

ubuntu/linux-nvidia-6.17<6.17.0-1008.8

6.17.0-1008.8

ubuntu/linux-nvidia-lowlatency<6.8.0-1049.52.1

6.8.0-1049.52.1

ubuntu/linux-nvidia-tegra<6.8.0-1020.20

6.8.0-1020.20

ubuntu/linux-oem-6.11*

ubuntu/linux-oem-6.14*

ubuntu/linux-oem-6.17<6.17.0-1011.11

6.17.0-1011.11

ubuntu/linux-oem-6.8*

ubuntu/linux-oracle<6.8.0-1047.48

6.8.0-1047.48

ubuntu/linux-oracle-6.14*

ubuntu/linux-oracle-6.17<6.17.0-1007.7~24.04.1

6.17.0-1007.7~24.04.1

ubuntu/linux-raspi<6.8.0-1050.54

6.8.0-1050.54

ubuntu/linux-raspi-realtime*

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-6.14*

ubuntu/linux-xilinx<6.8.0-1028.29

6.8.0-1028.29

ubuntu/linux-bluefield<6.8.0-1017.21

6.8.0-1017.21

ubuntu/linux-raspi-realtime<6.8.0-2040.41

6.8.0-2040.41

ubuntu/linux-realtime<6.8.1-1045.46

6.8.1-1045.46

ubuntu/linux-realtime-6.14*

ubuntu/linux-realtime-6.17<6.17.0-1006.7~24.04.1

6.17.0-1006.7~24.04.1

ubuntu/linux-aws-fips<6.8.0-1050.53+fips1

6.8.0-1050.53+fips1

ubuntu/linux-azure-fips<6.8.0-1052.58+fips1

6.8.0-1052.58+fips1

ubuntu/linux-fips<6.8.0-106.106+fips1

6.8.0-106.106+fips1

ubuntu/linux-gcp-fips<6.8.0-1052.55+fips1

6.8.0-1052.55+fips1

ubuntu/linux<6.17.0-14.14

6.17.0-14.14

ubuntu/linux-aws<6.17.0-1007.7

6.17.0-1007.7

ubuntu/linux-azure<6.17.0-1008.8

6.17.0-1008.8

ubuntu/linux-azure-fde*

ubuntu/linux-gcp<6.17.0-1007.7

6.17.0-1007.7

ubuntu/linux-oracle<6.17.0-1007.7

6.17.0-1007.7

ubuntu/linux-raspi<6.17.0-1008.8

6.17.0-1008.8

ubuntu/linux-realtime<6.17.0-1006.7

6.17.0-1006.7

ubuntu/linux-riscv<6.17.0-14.14.1

6.17.0-14.14.1

ubuntu/linux-vmware*

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade ubuntu/linux-aws-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1050.53~22.04.1
Upgrade
Upgrade ubuntu/linux-azure-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1051.57~22.04.1
Upgrade
Upgrade ubuntu/linux-azure-fde-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1058.65~22.04.1
Upgrade
Upgrade ubuntu/linux-gcp-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1052.55~22.04.1
Upgrade
Upgrade ubuntu/linux-hwe-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-106.106~22.04.1
Upgrade
Upgrade ubuntu/linux-ibm-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1049.49~22.04.1
Upgrade
Upgrade ubuntu/linux-lowlatency-hwe-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-106.106.1~22.04.1
Upgrade
Upgrade ubuntu/linux-nvidia-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1049.52~22.04.1
Upgrade
Upgrade ubuntu/linux-oracle-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1047.48~22.04.1
Upgrade
Upgrade ubuntu/linux-riscv-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-106.106~22.04.1
Upgrade
Upgrade ubuntu/linux-realtime-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.1-1045.46~22.04.1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 6.8.0-106.106
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 6.8.0-1050.53
Upgrade
Upgrade ubuntu/linux-aws-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1007.7~24.04.1
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 6.8.0-1051.57
Upgrade
Upgrade ubuntu/linux-azure-fde to a version that resolves this vulnerability.
Fixed in 6.8.0-1058.65
Upgrade
Upgrade ubuntu/linux-azure-nvidia to a version that resolves this vulnerability.
Fixed in 6.8.0-1039.42
Upgrade
Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 6.8.0-1052.55
Upgrade
Upgrade ubuntu/linux-gcp-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1008.8~24.04.1
Upgrade
Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.
Fixed in 6.8.0-1048.53
Upgrade
Upgrade ubuntu/linux-gkeop to a version that resolves this vulnerability.
Fixed in 6.8.0-1035.38
Upgrade
Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.
Fixed in 6.8.0-1049.49
Upgrade
Upgrade ubuntu/linux-lowlatency to a version that resolves this vulnerability.
Fixed in 6.8.0-106.106.1
Upgrade
Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.
Fixed in 6.8.0-1049.52
Upgrade
Upgrade ubuntu/linux-nvidia-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1008.8
Upgrade
Upgrade ubuntu/linux-nvidia-lowlatency to a version that resolves this vulnerability.
Fixed in 6.8.0-1049.52.1
Upgrade
Upgrade ubuntu/linux-nvidia-tegra to a version that resolves this vulnerability.
Fixed in 6.8.0-1020.20
Upgrade
Upgrade ubuntu/linux-oem-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1011.11
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 6.8.0-1047.48
Upgrade
Upgrade ubuntu/linux-oracle-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1007.7~24.04.1
Upgrade
Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.
Fixed in 6.8.0-1050.54
Upgrade
Upgrade ubuntu/linux-xilinx to a version that resolves this vulnerability.
Fixed in 6.8.0-1028.29
Upgrade
Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.
Fixed in 6.8.0-1017.21
Upgrade
Upgrade ubuntu/linux-raspi-realtime to a version that resolves this vulnerability.
Fixed in 6.8.0-2040.41
Upgrade
Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.
Fixed in 6.8.1-1045.46
Upgrade
Upgrade ubuntu/linux-realtime-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1006.7~24.04.1
Upgrade
Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-1050.53+fips1
Upgrade
Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-1052.58+fips1
Upgrade
Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-106.106+fips1
Upgrade
Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-1052.55+fips1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 6.17.0-14.14
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 6.17.0-1007.7
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 6.17.0-1008.8
Upgrade
Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 6.17.0-1007.7
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 6.17.0-1007.7
Upgrade
Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.
Fixed in 6.17.0-1008.8
Upgrade
Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.
Fixed in 6.17.0-1006.7
Upgrade
Upgrade ubuntu/linux-riscv to a version that resolves this vulnerability.
Fixed in 6.17.0-14.14.1

Event History

Dec 6, 2025

CVE Published

via MITRE·09:51 PM

Data Sourced

via MITRE·09:51 PM

DescriptionSeverity

Data Sourced

via OSV·10:15 PM

DescriptionSeverityAffected Software

Data Sourced

via NVD·10:15 PM

DescriptionSeverity

Dec 8, 2025

Data Sourced

via Microsoft·01:05 AM

DescriptionSeverityWeakness

Frequently Asked Questions

What is the severity of CVE-2025-40285?

CVE-2025-40285 has a medium severity level due to the potential for a reference count leak in session handling.

How do I fix CVE-2025-40285?

To fix CVE-2025-40285, update your Linux kernel to the latest stable version where the vulnerability has been resolved.

What impact does CVE-2025-40285 have on my system?

CVE-2025-40285 can lead to resource leaks, which may ultimately affect system stability and performance.

Is CVE-2025-40285 exploitable remotely?

CVE-2025-40285 is not classified as a remote exploit, as it pertains to session management within the kernel.

When was CVE-2025-40285 discovered?

CVE-2025-40285 was identified and documented as part of vulnerabilities addressed in the Linux kernel.

CVE-2025-40285: smb/server: fix possible refcount leak in smb2_sess_setup()

Affected Software

Remediation

Event History

Frequently Asked Questions

What is the severity of CVE-2025-40285?

How do I fix CVE-2025-40285?

What impact does CVE-2025-40285 have on my system?

Is CVE-2025-40285 exploitable remotely?

When was CVE-2025-40285 discovered?

Company

Resources

Contact