CVE-2026-31681: netfilter: xt_multiport: validate range encoding in checkentry

Q: What is the severity of CVE-2026-31681?

CVE-2026-31681 is classified as a potential denial-of-service vulnerability in the netfilter xt_multiport module of the Linux kernel.

Q: How do I fix CVE-2026-31681?

To fix CVE-2026-31681, upgrade the Linux kernel to a version that includes the security patch for this vulnerability.

Q: Which Linux kernel versions are affected by CVE-2026-31681?

CVE-2026-31681 affects certain versions of the Linux kernel that utilize the netfilter xt_multiport module.

Q: What impact does CVE-2026-31681 have on system security?

CVE-2026-31681 can lead to denial-of-service conditions, affecting the availability of services on the impacted system.

Q: Is CVE-2026-31681 being exploited in the wild?

As of the latest updates, there have been no confirmed reports of exploitation of CVE-2026-31681 in the wild.

Published Apr 25, 2026

Updated

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

netfilter: xtmultiport: validate range encoding in checkentry

portsmatchv1() treats any non-zero pflags entry as the start of a port range and unconditionally consumes the next ports[] element as the range end.

The checkentry path currently validates protocol, flags and count, but it does not validate the range encoding itself. As a result, malformed rules can mark the last slot as a range start or place two range starts back to back, leaving portsmatchv1() to step past the last valid ports[] element while interpreting the rule.

Reject malformed multiport v1 rules in checkentry by validating that each range start has a following element and that the following element is not itself marked as another range start.

Affected Software

256 affected componentsFixes available

Linux Linux kernel (netfilter xt_multiport)

Microsoft azl3 kernel 6.6.134.1-2

Patch available

Linux Linux kernel>=2.6.17<6.6.136

Linux Linux kernel>=6.7<6.12.83

Linux Linux kernel>=6.13<6.18.24

Linux Linux kernel>=6.19<6.19.14

Linux Linux kernel=7.0-rc1

Linux Linux kernel=7.0-rc2

Linux Linux kernel=7.0-rc3

Linux Linux kernel=7.0-rc4

Linux Linux kernel=7.0-rc5

Linux Linux kernel=7.0-rc6

Linux Linux kernel=7.0-rc7

debian/linux

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

ubuntu/linux*

ubuntu/linux-aws*

ubuntu/linux-azure*

ubuntu/linux-lts-xenial*

ubuntu/linux*

ubuntu/linux-aws*

ubuntu/linux-aws-hwe*

ubuntu/linux-azure*

ubuntu/linux-gcp*

ubuntu/linux-hwe*

ubuntu/linux-hwe-edge*

ubuntu/linux-kvm*

ubuntu/linux-oracle*

ubuntu/linux-fips*

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*

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ubuntu/linux-azure-edge*

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ubuntu/linux-gke-4.15*

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ubuntu/linux-oem*

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ubuntu/linux-oracle-5.0*

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ubuntu/linux-raspi-5.4*

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

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ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

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

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ubuntu/linux-gcp-5.8*

ubuntu/linux-gke*

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ubuntu/linux-ibm*

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

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ubuntu/linux-iot*

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5.15.0-1064.66~20.04.1

ubuntu/linux-oem-5.10*

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ubuntu/linux-oracle-5.8*

ubuntu/linux-raspi*

ubuntu/linux-raspi2*

ubuntu/linux-riscv*

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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*

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ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux<5.15.0-186.196

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ubuntu/linux-allwinner-5.19*

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ubuntu/linux-aws-5.19*

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ubuntu/linux-azure<5.15.0-1117.126

5.15.0-1117.126

ubuntu/linux-azure-5.19*

ubuntu/linux-azure-6.2*

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ubuntu/linux-azure-fde<5.15.0-1117.126

5.15.0-1117.126

ubuntu/linux-azure-fde-5.19*

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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*

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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*

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6.8.0-136.136~22.04.1

ubuntu/linux-ibm<5.15.0-1106.110

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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

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

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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

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5.15.0-1117.126+fips1

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5.15.0-186.196+fips1

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5.15.0-1112.122+fips1

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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*

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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-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

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ubuntu/linux-raspi-realtime<6.8.0-2050.52

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ubuntu/linux-realtime<6.8.1-1056.57

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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-nvidia<7.0.0-1006.6

7.0.0-1006.6

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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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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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
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Fixed in 5.15.0-1111.120
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Fixed in 6.8.1-1056.57~22.04.2
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Fixed in 5.15.0-1112.119+fips1
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Fixed in 5.15.0-1117.126+fips1
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Fixed in 5.15.0-186.196+fips1
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Fixed in 5.15.0-1112.122+fips1
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Fixed in 6.8.0-136.136
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Fixed in 6.8.0-1061.64
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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 6.8.0-1061.62
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Fixed in 6.8.0-136.136.2
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Fixed in 6.8.0-1059.62
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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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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
Upgrade
Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.
Fixed in 7.0.0-1006.6

Event History

Apr 25, 2026

CVE Published

via MITRE·08:46 AM

Data Sourced

via MITRE·08:46 AM

Description

Data Sourced

via OSV·09:16 AM

DescriptionSeverityAffected Software

Event

via OSV·09:16 AM

Data Sourced

via NVD·09:16 AM

RemedyDescriptionSeverityAffected Software

Apr 26, 2026

Data Sourced

via Microsoft·08:08 AM

DescriptionSeverityWeaknessAffected Software

Parent advisories

This vulnerability appears in the following advisories.

DSA-6238

Peer vulnerabilities

Found alongside the following vulnerabilities.

Frequently Asked Questions

What is the severity of CVE-2026-31681?

CVE-2026-31681 is classified as a potential denial-of-service vulnerability in the netfilter xt_multiport module of the Linux kernel.

How do I fix CVE-2026-31681?

To fix CVE-2026-31681, upgrade the Linux kernel to a version that includes the security patch for this vulnerability.

Which Linux kernel versions are affected by CVE-2026-31681?

CVE-2026-31681 affects certain versions of the Linux kernel that utilize the netfilter xt_multiport module.

What impact does CVE-2026-31681 have on system security?

CVE-2026-31681 can lead to denial-of-service conditions, affecting the availability of services on the impacted system.

Is CVE-2026-31681 being exploited in the wild?

As of the latest updates, there have been no confirmed reports of exploitation of CVE-2026-31681 in the wild.

CVE-2026-31681: netfilter: xt_multiport: validate range encoding in checkentry

Affected Software

Remediation

Event History

Parent advisories

Peer vulnerabilities

Frequently Asked Questions

What is the severity of CVE-2026-31681?

How do I fix CVE-2026-31681?

Which Linux kernel versions are affected by CVE-2026-31681?

What impact does CVE-2026-31681 have on system security?

Is CVE-2026-31681 being exploited in the wild?

Company

Resources

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