CVE-2026-31617: usb: gadget: f_ncm: validate minimum block_len in ncm_unwrap_ntb()

Q: Who can exploit this issue?

An attacker must act as a malicious USB host communicating with a system using the Linux kernel's USB gadget NCM function (f_ncm). The CVSS vector indicates local access and low privileges are required; no user interaction is required.

Q: What is the impact of a successful exploit?

A malicious host can provide crafted NTB headers and offsets that cause adjacent kernel memory to be copied into a network skb. The reported CVSS impact is limited to availability, with no confidentiality or integrity impact listed.

Q: Is a default configuration affected?

The issue is relevant when the USB gadget NCM function, f_ncm, is in use. The provided data does not establish whether that function is enabled or configured by default.

Q: What change addresses the issue?

The fix rejects NTB block lengths too small to contain at least the NTB header and one NDP. This prevents unsigned underflow in NDP and datagram bounds checks.

Published Apr 24, 2026

Updated

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

usb: gadget: fncm: validate minimum blocklen in ncmunwrapntb()

The blocklen read from the host-supplied NTB header is checked against ntbmax but has no lower bound. When blocklen is smaller than opts->ndpsize, the bounds check of: ndpindex > (blocklen - opts->ndpsize) will underflow producing a huge unsigned value that ndpindex can never exceed, defeating the check entirely.

The same underflow occurs in the datagram index checks against blocklen - opts->dpesize. With those checks neutered, a malicious USB host can choose ndpindex and datagram offsets that point past the actual transfer, and the skbputdata() copies adjacent kernel memory into the network skb.

Fix this by rejecting block lengths that cannot hold at least the NTB header plus one NDP. This will make blocklen - opts->ndpsize and blocklen - opts->dpesize both well-defined.

Commit 8d2b1a1ec9f5 ("CDC-NCM: avoid overflow in sanity checking") fixed a related class of issues on the host side of NCM.

Affected Software

245 affected componentsFixes available

Linux Linux kernel (f_ncm)

Linux Linux kernel>=5.9<6.6.136

Linux Linux kernel>=6.12<6.12.83

Linux Linux kernel>=6.13<6.18.24

Linux Linux kernel>=6.19<6.19.14

Linux Linux kernel>=7.0<7.0.1

debian/linux

6.1.176-16.1.190-16.12.107-16.12.115-27.2.12-17.2.15-1

ubuntu/linux-azure*

ubuntu/linux-aws-hwe*

ubuntu/linux-azure*

ubuntu/linux-gcp*

ubuntu/linux-hwe*

ubuntu/linux-hwe-edge*

ubuntu/linux-oracle*

ubuntu/linux*

ubuntu/linux-aws*

ubuntu/linux-aws-5.0*

ubuntu/linux-aws-5.3*

ubuntu/linux-aws-5.4*

ubuntu/linux-azure*

ubuntu/linux-azure-4.15*

ubuntu/linux-azure-5.3*

ubuntu/linux-azure-5.4*

ubuntu/linux-azure-edge*

ubuntu/linux-gcp*

ubuntu/linux-gcp-4.15*

ubuntu/linux-gcp-5.3*

ubuntu/linux-gcp-5.4*

ubuntu/linux-gke-4.15*

ubuntu/linux-gke-5.4*

ubuntu/linux-gkeop-5.4*

ubuntu/linux-hwe*

ubuntu/linux-hwe-5.4*

ubuntu/linux-hwe-edge*

ubuntu/linux-ibm-5.4*

ubuntu/linux-kvm*

ubuntu/linux-oem*

ubuntu/linux-oracle*

ubuntu/linux-oracle-5.0*

ubuntu/linux-oracle-5.3*

ubuntu/linux-oracle-5.4*

ubuntu/linux-raspi-5.4*

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux*

ubuntu/linux-aws*

ubuntu/linux-aws-5.11*

ubuntu/linux-aws-5.13*

ubuntu/linux-aws-5.15<5.15.0-1112.119~20.04.1

5.15.0-1112.119~20.04.1

ubuntu/linux-aws-5.8*

ubuntu/linux-azure*

ubuntu/linux-azure-5.11*

ubuntu/linux-azure-5.13*

ubuntu/linux-azure-5.15<5.15.0-1117.126~20.04.1

5.15.0-1117.126~20.04.1

ubuntu/linux-azure-5.8*

ubuntu/linux-azure-fde*

ubuntu/linux-azure-fde-5.15<5.15.0-1117.126~20.04.2

5.15.0-1117.126~20.04.2

ubuntu/linux-bluefield*

ubuntu/linux-gcp*

ubuntu/linux-gcp-5.11*

ubuntu/linux-gcp-5.13*

ubuntu/linux-gcp-5.15<5.15.0-1112.122~20.04.1

5.15.0-1112.122~20.04.1

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<5.15.0-186.196~20.04.1

5.15.0-186.196~20.04.1

ubuntu/linux-hwe-5.8*

ubuntu/linux-ibm*

ubuntu/linux-ibm-5.15<5.15.0-1106.110~20.04.1

5.15.0-1106.110~20.04.1

ubuntu/linux-intel-5.13*

ubuntu/linux-intel-iotg-5.15<5.15.0-1107.113~20.04.1

5.15.0-1107.113~20.04.1

ubuntu/linux-iot*

ubuntu/linux-kvm*

ubuntu/linux-lowlatency-hwe-5.15<5.15.0-184.194~20.04.1

5.15.0-184.194~20.04.1

ubuntu/linux-nvidia-tegra-5.15<5.15.0-1064.66~20.04.1

5.15.0-1064.66~20.04.1

ubuntu/linux-oem-5.10*

ubuntu/linux-oem-5.13*

ubuntu/linux-oem-5.6*

ubuntu/linux-oracle*

ubuntu/linux-oracle-5.11*

ubuntu/linux-oracle-5.13*

ubuntu/linux-oracle-5.15<5.15.0-1109.115~20.04.1

5.15.0-1109.115~20.04.1

ubuntu/linux-oracle-5.8*

ubuntu/linux-raspi*

ubuntu/linux-raspi2*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.11*

ubuntu/linux-riscv-5.15<5.15.0-1106.110~20.04.1

5.15.0-1106.110~20.04.1

ubuntu/linux-riscv-5.8*

ubuntu/linux-xilinx-zynqmp*

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux-fips*

ubuntu/linux<5.15.0-186.196

5.15.0-186.196

ubuntu/linux-allwinner-5.19*

ubuntu/linux-aws<5.15.0-1112.119

5.15.0-1112.119

ubuntu/linux-aws-5.19*

ubuntu/linux-aws-6.2*

ubuntu/linux-aws-6.5*

ubuntu/linux-aws-6.8<6.8.0-1061.64~22.04.1

6.8.0-1061.64~22.04.1

ubuntu/linux-azure<5.15.0-1117.126

5.15.0-1117.126

ubuntu/linux-azure-5.19*

ubuntu/linux-azure-6.2*

ubuntu/linux-azure-6.5*

ubuntu/linux-azure-6.8<6.8.0-1063.71~22.04.1

6.8.0-1063.71~22.04.1

ubuntu/linux-azure-fde<5.15.0-1117.126

5.15.0-1117.126

ubuntu/linux-azure-fde-5.19*

ubuntu/linux-azure-fde-6.2*

ubuntu/linux-azure-fde-6.8<6.8.0-1062.69~22.04.1

6.8.0-1062.69~22.04.1

ubuntu/linux-gcp<5.15.0-1112.122

5.15.0-1112.122

ubuntu/linux-gcp-5.19*

ubuntu/linux-gcp-6.2*

ubuntu/linux-gcp-6.5*

ubuntu/linux-gcp-6.8<6.8.0-1064.72~22.04.1

6.8.0-1064.72~22.04.1

ubuntu/linux-gke<5.15.0-1108.114

5.15.0-1108.114

ubuntu/linux-gkeop<5.15.0-1095.103

5.15.0-1095.103

ubuntu/linux-hwe-5.19*

ubuntu/linux-hwe-6.2*

ubuntu/linux-hwe-6.5*

ubuntu/linux-hwe-6.8<6.8.0-136.136~22.04.1

6.8.0-136.136~22.04.1

ubuntu/linux-ibm<5.15.0-1106.110

5.15.0-1106.110

ubuntu/linux-ibm-6.8<6.8.0-1061.62~22.04.1

6.8.0-1061.62~22.04.1

ubuntu/linux-intel-iot-realtime*

ubuntu/linux-intel-iotg<5.15.0-1107.113

5.15.0-1107.113

ubuntu/linux-kvm<5.15.0-1104.109

5.15.0-1104.109

ubuntu/linux-lowlatency<5.15.0-184.194

5.15.0-184.194

ubuntu/linux-lowlatency-hwe-5.19*

ubuntu/linux-lowlatency-hwe-6.2*

ubuntu/linux-lowlatency-hwe-6.5*

ubuntu/linux-lowlatency-hwe-6.8<6.8.0-136.136.2~22.04.1

6.8.0-136.136.2~22.04.1

ubuntu/linux-nvidia<5.15.0-1107.108

5.15.0-1107.108

ubuntu/linux-nvidia-6.2*

ubuntu/linux-nvidia-6.5*

ubuntu/linux-nvidia-6.8<6.8.0-1059.62~22.04.1

6.8.0-1059.62~22.04.1

ubuntu/linux-nvidia-tegra<5.15.0-1064.66

5.15.0-1064.66

ubuntu/linux-nvidia-tegra-igx<5.15.0-1053.53

5.15.0-1053.53

ubuntu/linux-oem-5.17*

ubuntu/linux-oem-6.0*

ubuntu/linux-oem-6.1*

ubuntu/linux-oem-6.5*

ubuntu/linux-oracle<5.15.0-1109.115

5.15.0-1109.115

ubuntu/linux-oracle-6.5*

ubuntu/linux-oracle-6.8<6.8.0-1058.61~22.04.1

6.8.0-1058.61~22.04.1

ubuntu/linux-raspi<5.15.0-1106.109

5.15.0-1106.109

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.19*

ubuntu/linux-riscv-6.5*

ubuntu/linux-riscv-6.8<6.8.0-136.136~22.04.3

6.8.0-136.136~22.04.3

ubuntu/linux-starfive-5.19*

ubuntu/linux-starfive-6.2*

ubuntu/linux-starfive-6.5*

ubuntu/linux-xilinx-zynqmp<5.15.0-1075.79

5.15.0-1075.79

ubuntu/linux-bluefield<5.15.0-1096.98

5.15.0-1096.98

ubuntu/linux-intel-iot-realtime<5.15.0-1104.106

5.15.0-1104.106

ubuntu/linux-realtime<5.15.0-1111.120

5.15.0-1111.120

ubuntu/linux-realtime-6.8<6.8.1-1056.57~22.04.2

6.8.1-1056.57~22.04.2

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux-aws-fips<5.15.0-1112.119+fips1

5.15.0-1112.119+fips1

ubuntu/linux-azure-fips<5.15.0-1117.126+fips1

5.15.0-1117.126+fips1

ubuntu/linux-fips<5.15.0-186.196+fips1

5.15.0-186.196+fips1

ubuntu/linux-gcp-fips<5.15.0-1112.122+fips1

5.15.0-1112.122+fips1

ubuntu/linux<6.8.0-136.136

6.8.0-136.136

ubuntu/linux-aws<6.8.0-1061.64

6.8.0-1061.64

ubuntu/linux-aws-6.14*

ubuntu/linux-aws-6.17*

ubuntu/linux-azure<6.8.0-1063.71

6.8.0-1063.71

ubuntu/linux-azure-6.11*

ubuntu/linux-azure-6.14*

ubuntu/linux-azure-6.17*

ubuntu/linux-azure-fde<6.8.0-1062.69

6.8.0-1062.69

ubuntu/linux-azure-fde-6.14*

ubuntu/linux-azure-nvidia*

ubuntu/linux-azure-nvidia-6.14*

ubuntu/linux-gcp<6.8.0-1064.72

6.8.0-1064.72

ubuntu/linux-gcp-6.11*

ubuntu/linux-gcp-6.14*

ubuntu/linux-gke<6.8.0-1059.67

6.8.0-1059.67

ubuntu/linux-gkeop<6.8.0-1046.50

6.8.0-1046.50

ubuntu/linux-hwe-6.11*

ubuntu/linux-hwe-6.14*

ubuntu/linux-hwe-6.17*

ubuntu/linux-hwe-7.0<7.0.0-28.28~24.04.1

7.0.0-28.28~24.04.1

ubuntu/linux-ibm<6.8.0-1061.62

6.8.0-1061.62

ubuntu/linux-lowlatency<6.8.0-136.136.2

6.8.0-136.136.2

ubuntu/linux-lowlatency-hwe-6.11*

ubuntu/linux-nvidia<6.8.0-1059.62

6.8.0-1059.62

ubuntu/linux-nvidia-6.11*

ubuntu/linux-nvidia-6.17*

ubuntu/linux-nvidia-lowlatency<6.8.0-1059.62.1

6.8.0-1059.62.1

ubuntu/linux-nvidia-tegra<6.8.0-1030.31

6.8.0-1030.31

ubuntu/linux-oem-6.11*

ubuntu/linux-oem-6.14*

ubuntu/linux-oem-6.17*

ubuntu/linux-oem-6.8*

ubuntu/linux-oracle<6.8.0-1058.61

6.8.0-1058.61

ubuntu/linux-oracle-6.14*

ubuntu/linux-oracle-6.17*

ubuntu/linux-raspi<6.8.0-1061.65

6.8.0-1061.65

ubuntu/linux-raspi-realtime*

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-6.14*

ubuntu/linux-riscv-6.17*

ubuntu/linux-xilinx<6.8.0-1033.34

6.8.0-1033.34

ubuntu/linux-bluefield<6.8.0-1028.33

6.8.0-1028.33

ubuntu/linux-raspi-realtime<6.8.0-2050.52

6.8.0-2050.52

ubuntu/linux-realtime<6.8.1-1056.57

6.8.1-1056.57

ubuntu/linux-realtime-6.14*

ubuntu/linux-realtime-6.17*

ubuntu/linux-aws-fips<6.8.0-1061.64+fips1

6.8.0-1061.64+fips1

ubuntu/linux-azure-fips<6.8.0-1063.71+fips2

6.8.0-1063.71+fips2

ubuntu/linux-fips<6.8.0-136.136+fips2

6.8.0-136.136+fips2

ubuntu/linux-gcp-fips<6.8.0-1064.72+fips1

6.8.0-1064.72+fips1

ubuntu/linux*

ubuntu/linux-aws*

ubuntu/linux-azure*

ubuntu/linux-azure-fde*

ubuntu/linux-gcp*

ubuntu/linux-oracle*

ubuntu/linux-raspi*

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux<7.0.0-27.27

7.0.0-27.27

ubuntu/linux-aws<7.0.0-1008.8

7.0.0-1008.8

ubuntu/linux-azure<7.0.0-1010.10

7.0.0-1010.10

ubuntu/linux-azure-fde<7.0.0-1009.9

7.0.0-1009.9

ubuntu/linux-gcp<7.0.0-1007.7

7.0.0-1007.7

ubuntu/linux-ibm<7.0.0-1009.9

7.0.0-1009.9

ubuntu/linux-nvidia<7.0.0-1013.13

7.0.0-1013.13

ubuntu/linux-oracle<7.0.0-1007.7

7.0.0-1007.7

ubuntu/linux-raspi<7.0.0-1014.14

7.0.0-1014.14

ubuntu/linux-realtime<7.0.0-27.27.1

7.0.0-27.27.1

ubuntu/linux-riscv<7.0.0-27.27.1

7.0.0-27.27.1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade debian/linux to a version that resolves this vulnerability.
Fixed in 6.1.176-1Fixed in 6.1.190-1Fixed in 6.12.107-1Fixed in 6.12.115-2Fixed in 7.2.12-1Fixed in 7.2.15-1
Upgrade
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Fixed in 5.15.0-1112.119~20.04.1
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Fixed in 5.15.0-1117.126~20.04.1
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Fixed in 5.15.0-1117.126~20.04.2
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Fixed in 5.15.0-1112.122~20.04.1
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Upgrade ubuntu/linux-hwe-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-186.196~20.04.1
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Fixed in 5.15.0-1106.110~20.04.1
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Fixed in 5.15.0-1107.113~20.04.1
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Upgrade ubuntu/linux-lowlatency-hwe-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-184.194~20.04.1
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Fixed in 5.15.0-1064.66~20.04.1
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Fixed in 5.15.0-1109.115~20.04.1
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Fixed in 5.15.0-1106.110~20.04.1
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Fixed in 5.15.0-186.196
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Fixed in 5.15.0-1112.119
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Fixed in 6.8.0-1061.64~22.04.1
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Fixed in 5.15.0-1117.126
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Fixed in 6.8.0-1063.71~22.04.1
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Fixed in 5.15.0-1117.126
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Fixed in 6.8.0-1062.69~22.04.1
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Fixed in 5.15.0-1112.122
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Fixed in 6.8.0-1064.72~22.04.1
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Fixed in 5.15.0-1108.114
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Fixed in 5.15.0-1095.103
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Fixed in 6.8.0-136.136~22.04.1
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Fixed in 5.15.0-1106.110
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Fixed in 6.8.0-1061.62~22.04.1
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Fixed in 5.15.0-1107.113
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Fixed in 5.15.0-1104.109
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Fixed in 5.15.0-184.194
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Fixed in 6.8.0-136.136.2~22.04.1
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Fixed in 5.15.0-1107.108
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Fixed in 6.8.0-1059.62~22.04.1
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Fixed in 5.15.0-1064.66
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Fixed in 5.15.0-1053.53
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Fixed in 5.15.0-1109.115
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Fixed in 6.8.0-1058.61~22.04.1
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Fixed in 5.15.0-1106.109
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Fixed in 6.8.0-136.136~22.04.3
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Fixed in 5.15.0-1075.79
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Fixed in 5.15.0-1096.98
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Fixed in 5.15.0-1104.106
Upgrade
Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.
Fixed in 5.15.0-1111.120
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Upgrade ubuntu/linux-realtime-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.1-1056.57~22.04.2
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Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-1112.119+fips1
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Fixed in 5.15.0-1117.126+fips1
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Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-186.196+fips1
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Fixed in 5.15.0-1112.122+fips1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 6.8.0-136.136
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Fixed in 6.8.0-1061.64
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Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 6.8.0-1063.71
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Fixed in 6.8.0-1062.69
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Fixed in 6.8.0-1064.72
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Fixed in 6.8.0-1059.67
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Fixed in 6.8.0-1046.50
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Fixed in 7.0.0-28.28~24.04.1
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Fixed in 6.8.0-1061.62
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Upgrade ubuntu/linux-lowlatency to a version that resolves this vulnerability.
Fixed in 6.8.0-136.136.2
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Fixed in 6.8.0-1059.62
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Upgrade ubuntu/linux-nvidia-lowlatency to a version that resolves this vulnerability.
Fixed in 6.8.0-1059.62.1
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Fixed in 6.8.0-1030.31
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Fixed in 6.8.0-1058.61
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Fixed in 6.8.0-1061.65
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Fixed in 6.8.0-1033.34
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Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.
Fixed in 6.8.0-1028.33
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Fixed in 6.8.0-2050.52
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Fixed in 6.8.1-1056.57
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Fixed in 6.8.0-1061.64+fips1
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Fixed in 6.8.0-1063.71+fips2
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Fixed in 6.8.0-136.136+fips2
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Fixed in 6.8.0-1064.72+fips1
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Fixed in 7.0.0-27.27
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Fixed in 7.0.0-1008.8
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Fixed in 7.0.0-1010.10
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Fixed in 7.0.0-1009.9
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Fixed in 7.0.0-1007.7
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Fixed in 7.0.0-1009.9
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Fixed in 7.0.0-1013.13
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Fixed in 7.0.0-1007.7
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Fixed in 7.0.0-1014.14
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Fixed in 7.0.0-27.27.1
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Fixed in 7.0.0-27.27.1

Event History

Apr 24, 2026

CVE Published

via MITRE·02:42 PM

Data Sourced

via MITRE·02:42 PM

Description

Data Sourced

via Red Hat·03:02 PM

DescriptionSeverityAffected Software

Data Sourced

via OSV·03:16 PM

DescriptionSeverityAffected Software

Event

via OSV·03:16 PM

Data Sourced

via NVD·03:16 PM

RemedyDescriptionSeverityWeaknessAffected Software

Apr 26, 2026

Data Sourced

via Microsoft·08:02 AM

DescriptionSeverityWeakness

Parent advisories

This vulnerability appears in the following advisories.

DSA-6238

Peer vulnerabilities

Found alongside the following vulnerabilities.

Frequently Asked Questions

Who can exploit this issue?

An attacker must act as a malicious USB host communicating with a system using the Linux kernel's USB gadget NCM function (f_ncm). The CVSS vector indicates local access and low privileges are required; no user interaction is required.

What is the impact of a successful exploit?

A malicious host can provide crafted NTB headers and offsets that cause adjacent kernel memory to be copied into a network skb. The reported CVSS impact is limited to availability, with no confidentiality or integrity impact listed.

Is a default configuration affected?

The issue is relevant when the USB gadget NCM function, f_ncm, is in use. The provided data does not establish whether that function is enabled or configured by default.

What change addresses the issue?

The fix rejects NTB block lengths too small to contain at least the NTB header and one NDP. This prevents unsigned underflow in NDP and datagram bounds checks.

CVE-2026-31617: usb: gadget: f_ncm: validate minimum block_len in ncm_unwrap_ntb()

Affected Software

Remediation

Event History

Parent advisories

Peer vulnerabilities

Frequently Asked Questions

Who can exploit this issue?

What is the impact of a successful exploit?

Is a default configuration affected?

What change addresses the issue?

Company

Resources

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