CVE-2026-31787: xen/privcmd: fix double free via VMA splitting

Q: What access and action are required to trigger this issue?

The issue is locally reachable and requires low privileges. A userspace process must perform a partial munmap() on a privcmd mapping, causing the kernel to split the associated VMA.

Q: Why does a partial unmap lead to a double free?

The VMA split duplicates the vm_private_data pointer without creating independent ownership of the pages array. Closing the unmapped portion frees that array, and destruction of the surviving VMA later attempts to free the same dangling pointer again.

Q: What is the security impact if the flaw is triggered?

The vulnerability is a double free with high confidentiality, integrity, and availability impact in the provided severity vector. It can affect Xen mapping cleanup through the privcmd driver.

Published Apr 28, 2026

Updated

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

xen/privcmd: fix double free via VMA splitting

privcmdvmops defines .close (privcmdclose), but neither .maysplit nor .open. When userspace does a partial munmap() on a privcmd mapping, the kernel splits the VMA via splitvma(). Since maysplit is NULL, the split is allowed. vmareadup() copies vmprivatedata (a pages array allocated in allocemptypages()) into the new VMA without any fixup, because there is no .open callback.

Both VMAs now point to the same pages array. When the unmapped portion is closed, privcmdclose() calls: - xenunmapdomaingfnrange() - xenfreeunpopulatedpages() - kvfree(pages)

The surviving VMA still holds the dangling pointer. When it is later destroyed, the same sequence runs again, which leads to a double free.

Fix this issue by adding a .maysplit callback denying the VMA split.

This is XSA-487 / CVE-2026-31787

Affected Software

266 affected componentsFixes available

Linux Linux kernel (xen/privcmd)

Linux Linux kernel>=3.8<5.10.254

Linux Linux kernel>=5.11<5.15.204

Linux Linux kernel>=5.16<6.1.170

Linux Linux kernel>=6.2<6.6.137

Linux Linux kernel>=6.7<6.12.85

Linux Linux kernel>=6.13<6.18.26

Linux Linux kernel>=6.19<7.0.3

Linux Linux kernel=7.1-rc1

Linux Linux kernel=7.1-rc2

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*

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-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-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-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

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ubuntu/linux-aws-5.19*

ubuntu/linux-aws-6.2*

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

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ubuntu/linux-azure<5.15.0-1117.126

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ubuntu/linux-azure-5.19*

ubuntu/linux-azure-6.2*

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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*

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-fde-6.17*

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-oem-7.0<7.0.0-1008.8

7.0.0-1008.8

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

debian/linux

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

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
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Fixed in 6.1.176-1Fixed in 6.1.190-1Fixed in 6.12.107-1Fixed in 6.12.113-1Fixed in 7.2.12-1Fixed in 7.2.14-1
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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 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 5.15.0-1053.53
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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 7.0.0-28.28~24.04.1
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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
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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 7.0.0-1008.8
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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
Configuration
Add a .may_split callback to privcmd_vm_ops that denies VMA splits.
Linux kernel Xen privcmd driver .may_split callback = deny VMA splitting

Event History

Apr 30, 2026

CVE Published

via MITRE·10:31 AM

Data Sourced

via MITRE·10:31 AM

Description

Data Sourced

via OSV·11:16 AM

DescriptionSeverityAffected Software

Data Sourced

via NVD·11:16 AM

RemedyDescriptionSeverityWeaknessAffected Software

Data Sourced

via Red Hat·12:01 PM

DescriptionSeverityAffected Software

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

Frequently Asked Questions

What access and action are required to trigger this issue?

The issue is locally reachable and requires low privileges. A userspace process must perform a partial munmap() on a privcmd mapping, causing the kernel to split the associated VMA.

Why does a partial unmap lead to a double free?

The VMA split duplicates the vm_private_data pointer without creating independent ownership of the pages array. Closing the unmapped portion frees that array, and destruction of the surviving VMA later attempts to free the same dangling pointer again.

What is the security impact if the flaw is triggered?

The vulnerability is a double free with high confidentiality, integrity, and availability impact in the provided severity vector. It can affect Xen mapping cleanup through the privcmd driver.

CVE-2026-31787: xen/privcmd: fix double free via VMA splitting

Affected Software

Remediation

Event History

Parent advisories

Peer vulnerabilities

Frequently Asked Questions

What access and action are required to trigger this issue?

Why does a partial unmap lead to a double free?

What is the security impact if the flaw is triggered?

Company

Resources

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