CVE-2026-45915: fat: avoid parent link count underflow in rmdir

Q: Who is exposed to this issue?

Systems using the Linux kernel with FAT filesystems are exposed when operating on a corrupted FAT image whose directory inode has an incorrect parent link count. The CVSS vector indicates exploitation requires local access and low privileges.

Q: What action triggers the problem?

Removing a directory with rmdir can trigger the issue when the affected directory's parent inode has an incorrect i_nlink value. The vulnerable code could decrement that count to zero and trigger a WARN_ON in drop_nlink().

Q: How does the fix change behavior for corrupted filesystems?

The updated vfat_rmdir() and msdos_rmdir() paths only decrement the parent link count when it is at least 3. Otherwise, they report a filesystem error rather than allowing the link count to underflow.

Published May 27, 2026

Updated

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

fat: avoid parent link count underflow in rmdir

Corrupted FAT images can leave a directory inode with an incorrect inlink (e.g. 2 even though subdirectories exist). rmdir then unconditionally calls dropnlink(dir) and can drive inlink to 0, triggering the WARNON in dropnlink().

Add a sanity check in vfatrmdir() and msdosrmdir(): only drop the parent link count when it is at least 3, otherwise report a filesystem error.

Affected Software

249 affected componentsFixes available

Linux Linux kernel

Linux Linux kernel>=2.6.19<5.10.252

Linux Linux kernel>=5.11<5.15.202

Linux Linux kernel>=5.16<6.1.165

Linux Linux kernel>=6.2<6.6.128

Linux Linux kernel>=6.7<6.12.75

Linux Linux kernel>=6.13<6.18.14

Linux Linux kernel>=6.19<6.19.4

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

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<6.8.0-1060.63~22.04.1

6.8.0-1060.63~22.04.1

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<6.8.0-1063.69~22.04.1

6.8.0-1063.69~22.04.1

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<6.8.0-1060.61~22.04.1

6.8.0-1060.61~22.04.1

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<6.8.0-134.134.1~22.04.1

6.8.0-134.134.1~22.04.1

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<6.8.0-1058.61~22.04.1

6.8.0-1058.61~22.04.1

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<6.8.0-1057.58~22.04.1

6.8.0-1057.58~22.04.1

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<6.8.0-134.134~22.04.1

6.8.0-134.134~22.04.1

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<6.8.1-1055.56~22.04.1

6.8.1-1055.56~22.04.1

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<6.8.0-134.134

6.8.0-134.134

ubuntu/linux-aws<6.8.0-1060.63

6.8.0-1060.63

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<6.8.0-1063.69

6.8.0-1063.69

ubuntu/linux-gcp-6.11*

ubuntu/linux-gcp-6.14*

ubuntu/linux-gke<6.8.0-1058.64

6.8.0-1058.64

ubuntu/linux-gkeop<6.8.0-1045.48

6.8.0-1045.48

ubuntu/linux-hwe-6.11*

ubuntu/linux-hwe-6.14*

ubuntu/linux-hwe-6.17*

ubuntu/linux-ibm<6.8.0-1060.61

6.8.0-1060.61

ubuntu/linux-lowlatency<6.8.0-134.134.1

6.8.0-134.134.1

ubuntu/linux-lowlatency-hwe-6.11*

ubuntu/linux-nvidia<6.8.0-1058.61

6.8.0-1058.61

ubuntu/linux-nvidia-6.11*

ubuntu/linux-nvidia-6.17*

ubuntu/linux-nvidia-lowlatency<6.8.0-1058.61.1

6.8.0-1058.61.1

ubuntu/linux-nvidia-tegra<6.8.0-1029.30

6.8.0-1029.30

ubuntu/linux-oem-6.11*

ubuntu/linux-oem-6.14*

ubuntu/linux-oem-6.17*

ubuntu/linux-oem-6.8*

ubuntu/linux-oracle<6.8.0-1057.58

6.8.0-1057.58

ubuntu/linux-oracle-6.14*

ubuntu/linux-oracle-6.17*

ubuntu/linux-raspi<6.8.0-1060.64

6.8.0-1060.64

ubuntu/linux-raspi-realtime*

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-6.14*

ubuntu/linux-riscv-6.17*

ubuntu/linux-xilinx<6.8.0-1032.33

6.8.0-1032.33

ubuntu/linux-bluefield<6.8.0-1026.30

6.8.0-1026.30

ubuntu/linux-raspi-realtime<6.8.0-2049.50

6.8.0-2049.50

ubuntu/linux-realtime<6.8.1-1055.56

6.8.1-1055.56

ubuntu/linux-realtime-6.14*

ubuntu/linux-realtime-6.17*

ubuntu/linux-aws-fips<6.8.0-1060.63+fips1

6.8.0-1060.63+fips1

ubuntu/linux-azure-fips<6.8.0-1062.69+fips1

6.8.0-1062.69+fips1

ubuntu/linux-fips<6.8.0-134.134+fips1

6.8.0-134.134+fips1

ubuntu/linux-gcp-fips<6.8.0-1063.69+fips1

6.8.0-1063.69+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*

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade ubuntu/linux-aws-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1112.119~20.04.1
Upgrade
Upgrade ubuntu/linux-azure-5.15 to a version that resolves this vulnerability.
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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Upgrade ubuntu/linux-intel-iotg-5.15 to a version that resolves this vulnerability.
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
Upgrade
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Fixed in 5.15.0-186.196
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Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 5.15.0-1112.119
Upgrade
Upgrade ubuntu/linux-aws-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1060.63~22.04.1
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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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Upgrade ubuntu/linux-gcp-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1063.69~22.04.1
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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 6.8.0-1060.61~22.04.1
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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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Upgrade ubuntu/linux-lowlatency to a version that resolves this vulnerability.
Fixed in 5.15.0-184.194
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Upgrade ubuntu/linux-lowlatency-hwe-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-134.134.1~22.04.1
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Fixed in 5.15.0-1107.108
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Fixed in 6.8.0-1058.61~22.04.1
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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 6.8.0-1057.58~22.04.1
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Fixed in 5.15.0-1106.109
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Fixed in 6.8.0-134.134~22.04.1
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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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Upgrade ubuntu/linux-intel-iot-realtime to a version that resolves this vulnerability.
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
Upgrade
Upgrade ubuntu/linux-realtime-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.1-1055.56~22.04.1
Upgrade
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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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Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-186.196+fips1
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Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-1112.122+fips1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 6.8.0-134.134
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Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 6.8.0-1060.63
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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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Upgrade ubuntu/linux-azure-fde to a version that resolves this vulnerability.
Fixed in 6.8.0-1062.69
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Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 6.8.0-1063.69
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Fixed in 6.8.0-1058.64
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Fixed in 6.8.0-1045.48
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Fixed in 6.8.0-1060.61
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Fixed in 6.8.0-134.134.1
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Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.
Fixed in 6.8.0-1058.61
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Upgrade ubuntu/linux-nvidia-lowlatency to a version that resolves this vulnerability.
Fixed in 6.8.0-1058.61.1
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Fixed in 6.8.0-1029.30
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Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 6.8.0-1057.58
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Fixed in 6.8.0-1060.64
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Fixed in 6.8.0-1032.33
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Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.
Fixed in 6.8.0-1026.30
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Fixed in 6.8.0-2049.50
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Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.
Fixed in 6.8.1-1055.56
Upgrade
Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-1060.63+fips1
Upgrade
Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-1062.69+fips1
Upgrade
Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-134.134+fips1
Upgrade
Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-1063.69+fips1
Compensating control
Add a sanity check in vfat_rmdir() and msdos_rmdir(): only decrement the parent link count when it is at least 3; otherwise report a filesystem error.

Event History

May 27, 2026

CVE Published

via MITRE·12:17 PM

Data Sourced

via MITRE·12:17 PM

Description

Data Sourced

via OSV·02:17 PM

DescriptionSeverityAffected Software

Event

via OSV·02:17 PM

Data Sourced

via NVD·02:17 PM

RemedyDescriptionSeverityAffected Software

Frequently Asked Questions

Who is exposed to this issue?

Systems using the Linux kernel with FAT filesystems are exposed when operating on a corrupted FAT image whose directory inode has an incorrect parent link count. The CVSS vector indicates exploitation requires local access and low privileges.

What action triggers the problem?

Removing a directory with rmdir can trigger the issue when the affected directory's parent inode has an incorrect i_nlink value. The vulnerable code could decrement that count to zero and trigger a WARN_ON in drop_nlink().

How does the fix change behavior for corrupted filesystems?

The updated vfat_rmdir() and msdos_rmdir() paths only decrement the parent link count when it is at least 3. Otherwise, they report a filesystem error rather than allowing the link count to underflow.

CVE-2026-45915: fat: avoid parent link count underflow in rmdir

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How does the fix change behavior for corrupted filesystems?

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