UBUNTU-CVE-2025-21991: High severity ubuntu/linux-hwe-edge vulnerability

Q: Which systems are exposed to the out-of-bounds access?

The affected condition requires an AMD system with CPU-less NUMA nodes, such as a machine using far memory, where a NUMA node has an empty CPU mask. The listed Ubuntu kernel packages include linux, linux-aws, linux-azure, linux-gcp, their relevant FIPS variants, and linux-realtime.

Q: What is required to trigger the issue?

A microcode update must be flashed on the affected AMD system. Flashing microcode is a privileged operation, so an attacker would need privileges sufficient to initiate that operation.

Q: Is this primarily a security exposure or a reliability issue?

The provided information states that it has no security implications because microcode flashing is privileged. The practical concern is reliability: the out-of-bounds per-CPU array access may corrupt memory while applying a microcode update.

Q: How can administrators identify the affected configuration?

Check whether the system is an AMD machine with NUMA nodes that contain memory but no CPUs, resulting in an empty CPU mask for a node. On kernels booted with CONFIG_UBSAN_BOUNDS=y, applying a microcode update can produce an array-index-out-of-bounds UBSAN report in the AMD microcode code.

Published Apr 2, 2025

Updated

In the Linux kernel, the following vulnerability has been resolved: x86/microcode/AMD: Fix out-of-bounds on systems with CPU-less NUMA nodes Currently, loadmicrocodeamd() iterates over all NUMA nodes, retrieves their CPU masks and unconditionally accesses per-CPU data for the first CPU of each mask. According to Documentation/admin-guide/mm/numaperf.rst: "Some memory may share the same node as a CPU, and others are provided as memory only nodes." Therefore, some node CPU masks may be empty and wouldn't have a "first CPU". On a machine with far memory (and therefore CPU-less NUMA nodes): - cpumaskofnode(nid) is 0 - cpumaskfirst(0) is CONFIGNRCPUS - cpudata(CONFIGNRCPUS) accesses the cpuinfo per-CPU array at an index that is 1 out of bounds This does not have any security implications since flashing microcode is a privileged operation but I believe this has reliability implications by potentially corrupting memory while flashing a microcode update. When booting with CONFIGUBSANBOUNDS=y on an AMD machine that flashes a microcode update. I get the following splat: UBSAN: array-index-out-of-bounds in arch/x86/kernel/cpu/microcode/amd.c:X:Y index 512 is out of range for type 'unsigned long[512]' [...] Call Trace: dumpstack ubsanhandleoutofbounds loadmicrocodeamd requestmicrocodeamd reloadstore kernfsfopwriteiter vfswrite ksyswrite dosyscall64 entrySYSCALL64afterhwframe Change the loop to go over only NUMA nodes which have CPUs before determining whether the first CPU on the respective node needs microcode update. [ bp: Massage commit message, fix typo. ]

Affected Software

179 affected componentsFixes available

ubuntu/linux-hwe-edge*

ubuntu/linux-aws-5.0*

ubuntu/linux-aws-5.3*

ubuntu/linux-aws-5.4<5.4.0-1147.157~18.04.1

5.4.0-1147.157~18.04.1

ubuntu/linux-azure*

ubuntu/linux-azure-5.3*

ubuntu/linux-azure-5.4<5.4.0-1152.159~18.04.1

5.4.0-1152.159~18.04.1

ubuntu/linux-azure-edge*

ubuntu/linux-gcp*

ubuntu/linux-gcp-5.3*

ubuntu/linux-gcp-5.4<5.4.0-1150.159~18.04.1

5.4.0-1150.159~18.04.1

ubuntu/linux-gke-4.15*

ubuntu/linux-gke-5.4*

ubuntu/linux-gkeop-5.4*

ubuntu/linux-hwe*

ubuntu/linux-hwe-5.4<5.4.0-218.238~18.04.1

5.4.0-218.238~18.04.1

ubuntu/linux-hwe-edge*

ubuntu/linux-ibm-5.4<5.4.0-1093.98~18.04.1

5.4.0-1093.98~18.04.1

ubuntu/linux-oem*

ubuntu/linux-oracle-5.0*

ubuntu/linux-oracle-5.3*

ubuntu/linux-oracle-5.4<5.4.0-1145.155~18.04.1

5.4.0-1145.155~18.04.1

ubuntu/linux-raspi-5.4<5.4.0-1130.143~18.04.1

5.4.0-1130.143~18.04.1

ubuntu/linux<5.4.0-218.238

5.4.0-218.238

ubuntu/linux-aws<5.4.0-1147.157

5.4.0-1147.157

ubuntu/linux-aws-5.11*

ubuntu/linux-aws-5.13*

ubuntu/linux-aws-5.15<5.15.0-1086.93~20.04.1

5.15.0-1086.93~20.04.1

ubuntu/linux-aws-5.8*

ubuntu/linux-azure<5.4.0-1152.159

5.4.0-1152.159

ubuntu/linux-azure-5.11*

ubuntu/linux-azure-5.13*

ubuntu/linux-azure-5.15<5.15.0-1091.100~20.04.1

5.15.0-1091.100~20.04.1

ubuntu/linux-azure-5.8*

ubuntu/linux-azure-fde*

ubuntu/linux-bluefield<5.4.0-1106.113

5.4.0-1106.113

ubuntu/linux-gcp<5.4.0-1150.159

5.4.0-1150.159

ubuntu/linux-gcp-5.11*

ubuntu/linux-gcp-5.13*

ubuntu/linux-gcp-5.15<5.15.0-1085.94~20.04.1

5.15.0-1085.94~20.04.1

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<5.15.0-142.152~20.04.1

5.15.0-142.152~20.04.1

ubuntu/linux-hwe-5.8*

ubuntu/linux-ibm<5.4.0-1093.98

5.4.0-1093.98

ubuntu/linux-ibm-5.15<5.15.0-1078.81~20.04.1

5.15.0-1078.81~20.04.1

ubuntu/linux-intel-5.13*

ubuntu/linux-intel-iotg-5.15<5.15.0-1083.89~20.04.1

5.15.0-1083.89~20.04.1

ubuntu/linux-iot<5.4.0-1051.54

5.4.0-1051.54

ubuntu/linux-kvm<5.4.0-1134.143

5.4.0-1134.143

ubuntu/linux-lowlatency-hwe-5.15<5.15.0-142.152~20.04.1

5.15.0-142.152~20.04.1

ubuntu/linux-nvidia-tegra-5.15<5.15.0-1039.39~20.04.1

5.15.0-1039.39~20.04.1

ubuntu/linux-oem-5.10*

ubuntu/linux-oem-5.13*

ubuntu/linux-oem-5.6*

ubuntu/linux-oracle<5.4.0-1145.155

5.4.0-1145.155

ubuntu/linux-oracle-5.11*

ubuntu/linux-oracle-5.13*

ubuntu/linux-oracle-5.15<5.15.0-1083.89~20.04.1

5.15.0-1083.89~20.04.1

ubuntu/linux-oracle-5.8*

ubuntu/linux-raspi<5.4.0-1130.143

5.4.0-1130.143

ubuntu/linux-raspi2*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.11*

ubuntu/linux-riscv-5.15<5.15.0-1081.85~20.04.1

5.15.0-1081.85~20.04.1

ubuntu/linux-riscv-5.8*

ubuntu/linux-xilinx-zynqmp<5.4.0-1065.69

5.4.0-1065.69

ubuntu/linux-aws-fips<5.4.0-1147.157+fips1

5.4.0-1147.157+fips1

ubuntu/linux-azure-fips<5.4.0-1153.160+fips1

5.4.0-1153.160+fips1

ubuntu/linux-fips<5.4.0-1121.131

5.4.0-1121.131

ubuntu/linux-gcp-fips<5.4.0-1150.159+fips1

5.4.0-1150.159+fips1

ubuntu/linux<5.15.0-142.152

5.15.0-142.152

ubuntu/linux-allwinner-5.19*

ubuntu/linux-aws<5.15.0-1086.93

5.15.0-1086.93

ubuntu/linux-aws-5.19*

ubuntu/linux-aws-6.2*

ubuntu/linux-aws-6.5*

ubuntu/linux-aws-6.8<6.8.0-1039.41~22.04.1

6.8.0-1039.41~22.04.1

ubuntu/linux-azure<5.15.0-1091.100

5.15.0-1091.100

ubuntu/linux-azure-5.19*

ubuntu/linux-azure-6.2*

ubuntu/linux-azure-6.5*

ubuntu/linux-azure-6.8<6.8.0-1036.42~22.04.1

6.8.0-1036.42~22.04.1

ubuntu/linux-azure-fde<5.15.0-1091.100.1

5.15.0-1091.100.1

ubuntu/linux-azure-fde-5.19*

ubuntu/linux-azure-fde-6.2*

ubuntu/linux-gcp<5.15.0-1085.94

5.15.0-1085.94

ubuntu/linux-gcp-5.19*

ubuntu/linux-gcp-6.2*

ubuntu/linux-gcp-6.5*

ubuntu/linux-gcp-6.8<6.8.0-1040.42~22.04.1

6.8.0-1040.42~22.04.1

ubuntu/linux-gke<5.15.0-1083.89

5.15.0-1083.89

ubuntu/linux-gkeop<5.15.0-1068.76

5.15.0-1068.76

ubuntu/linux-hwe-5.19*

ubuntu/linux-hwe-6.2*

ubuntu/linux-hwe-6.5*

ubuntu/linux-hwe-6.8<6.8.0-85.85~22.04.1

6.8.0-85.85~22.04.1

ubuntu/linux-ibm<5.15.0-1078.81

5.15.0-1078.81

ubuntu/linux-ibm-6.8<6.8.0-1037.37~22.04.1

6.8.0-1037.37~22.04.1

ubuntu/linux-intel-iot-realtime*

ubuntu/linux-intel-iotg<5.15.0-1081.87

5.15.0-1081.87

ubuntu/linux-kvm<5.15.0-1082.87

5.15.0-1082.87

ubuntu/linux-lowlatency<5.15.0-142.152

5.15.0-142.152

ubuntu/linux-lowlatency-hwe-5.19*

ubuntu/linux-lowlatency-hwe-6.2*

ubuntu/linux-lowlatency-hwe-6.5*

ubuntu/linux-lowlatency-hwe-6.8<6.8.0-84.84.1~22.04.1

6.8.0-84.84.1~22.04.1

ubuntu/linux-nvidia<5.15.0-1080.81

5.15.0-1080.81

ubuntu/linux-nvidia-6.2*

ubuntu/linux-nvidia-6.5*

ubuntu/linux-nvidia-6.8<6.8.0-1039.42~22.04.1

6.8.0-1039.42~22.04.1

ubuntu/linux-nvidia-tegra<5.15.0-1039.39

5.15.0-1039.39

ubuntu/linux-nvidia-tegra-igx<5.15.0-1028.28

5.15.0-1028.28

ubuntu/linux-oem-5.17*

ubuntu/linux-oem-6.0*

ubuntu/linux-oem-6.1*

ubuntu/linux-oem-6.5*

ubuntu/linux-oracle<5.15.0-1083.89

5.15.0-1083.89

ubuntu/linux-oracle-6.5*

ubuntu/linux-oracle-6.8<6.8.0-1037.38~22.04.1

6.8.0-1037.38~22.04.1

ubuntu/linux-raspi<5.15.0-1080.83

5.15.0-1080.83

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.19*

ubuntu/linux-riscv-6.5*

ubuntu/linux-riscv-6.8<6.8.0-84.84~22.04.1

6.8.0-84.84~22.04.1

ubuntu/linux-starfive-5.19*

ubuntu/linux-starfive-6.2*

ubuntu/linux-starfive-6.5*

ubuntu/linux-xilinx-zynqmp<5.15.0-1050.54

5.15.0-1050.54

ubuntu/linux-bluefield<5.15.0-1069.71

5.15.0-1069.71

ubuntu/linux-intel-iot-realtime<5.15.0-1079.81

5.15.0-1079.81

ubuntu/linux-realtime<5.15.0-1086.95

5.15.0-1086.95

ubuntu/linux-realtime-6.8<6.8.1-1034.35~22.04.1

6.8.1-1034.35~22.04.1

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux-aws-fips<5.15.0-1086.93+fips1

5.15.0-1086.93+fips1

ubuntu/linux-azure-fips<5.15.0-1091.100+fips1

5.15.0-1091.100+fips1

ubuntu/linux-fips<5.15.0-142.152+fips1

5.15.0-142.152+fips1

ubuntu/linux-gcp-fips<5.15.0-1085.94+fips1

5.15.0-1085.94+fips1

ubuntu/linux<6.8.0-84.84

6.8.0-84.84

ubuntu/linux-aws<6.8.0-1039.41

6.8.0-1039.41

ubuntu/linux-azure<6.8.0-1038.44

6.8.0-1038.44

ubuntu/linux-azure-6.11<6.11.0-1018.18~24.04.1

6.11.0-1018.18~24.04.1

ubuntu/linux-azure-nvidia<6.8.0-1025.27

6.8.0-1025.27

ubuntu/linux-gcp<6.8.0-1040.42

6.8.0-1040.42

ubuntu/linux-gcp-6.11<6.11.0-1016.16~24.04.1

6.11.0-1016.16~24.04.1

ubuntu/linux-gke<6.8.0-1036.40

6.8.0-1036.40

ubuntu/linux-gkeop<6.8.0-1023.25

6.8.0-1023.25

ubuntu/linux-hwe-6.11<6.11.0-28.28~24.04.1

6.11.0-28.28~24.04.1

ubuntu/linux-ibm<6.8.0-1037.37

6.8.0-1037.37

ubuntu/linux-intel*

ubuntu/linux-lowlatency<6.8.0-84.84.1

6.8.0-84.84.1

ubuntu/linux-lowlatency-hwe-6.11<6.11.0-1015.16~24.04.2

6.11.0-1015.16~24.04.2

ubuntu/linux-nvidia<6.8.0-1039.42

6.8.0-1039.42

ubuntu/linux-nvidia-6.11<6.11.0-1012.12

6.11.0-1012.12

ubuntu/linux-nvidia-lowlatency<6.8.0-1039.42.1

6.8.0-1039.42.1

ubuntu/linux-nvidia-tegra<6.8.0-1010.10

6.8.0-1010.10

ubuntu/linux-oem-6.11<6.11.0-1024.24

6.11.0-1024.24

ubuntu/linux-oem-6.8*

ubuntu/linux-oracle<6.8.0-1037.38

6.8.0-1037.38

ubuntu/linux-raspi<6.8.0-1039.43

6.8.0-1039.43

ubuntu/linux-raspi-realtime*

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-xilinx<6.8.0-1018.19

6.8.0-1018.19

ubuntu/linux-raspi-realtime<6.8.0-2030.31

6.8.0-2030.31

ubuntu/linux-realtime<6.8.1-1034.35

6.8.1-1034.35

ubuntu/linux-aws-fips<6.8.0-1039.41+fips1

6.8.0-1039.41+fips1

ubuntu/linux-azure-fips<6.8.0-1040.46+fips1

6.8.0-1040.46+fips1

ubuntu/linux-fips<6.8.0-84.84+fips1

6.8.0-84.84+fips1

ubuntu/linux-gcp-fips<6.8.0-1040.42+fips1

6.8.0-1040.42+fips1

ubuntu/linux-vmware*

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade ubuntu/linux-aws-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1147.157~18.04.1
Upgrade
Upgrade ubuntu/linux-azure-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1152.159~18.04.1
Upgrade
Upgrade ubuntu/linux-gcp-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1150.159~18.04.1
Upgrade
Upgrade ubuntu/linux-hwe-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-218.238~18.04.1
Upgrade
Upgrade ubuntu/linux-ibm-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1093.98~18.04.1
Upgrade
Upgrade ubuntu/linux-oracle-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1145.155~18.04.1
Upgrade
Upgrade ubuntu/linux-raspi-5.4 to a version that resolves this vulnerability.
Fixed in 5.4.0-1130.143~18.04.1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 5.4.0-218.238
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 5.4.0-1147.157
Upgrade
Upgrade ubuntu/linux-aws-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1086.93~20.04.1
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 5.4.0-1152.159
Upgrade
Upgrade ubuntu/linux-azure-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1091.100~20.04.1
Upgrade
Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.
Fixed in 5.4.0-1106.113
Upgrade
Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 5.4.0-1150.159
Upgrade
Upgrade ubuntu/linux-gcp-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1085.94~20.04.1
Upgrade
Upgrade ubuntu/linux-hwe-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-142.152~20.04.1
Upgrade
Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.
Fixed in 5.4.0-1093.98
Upgrade
Upgrade ubuntu/linux-ibm-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1078.81~20.04.1
Upgrade
Upgrade ubuntu/linux-intel-iotg-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1083.89~20.04.1
Upgrade
Upgrade ubuntu/linux-iot to a version that resolves this vulnerability.
Fixed in 5.4.0-1051.54
Upgrade
Upgrade ubuntu/linux-kvm to a version that resolves this vulnerability.
Fixed in 5.4.0-1134.143
Upgrade
Upgrade ubuntu/linux-lowlatency-hwe-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-142.152~20.04.1
Upgrade
Upgrade ubuntu/linux-nvidia-tegra-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1039.39~20.04.1
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 5.4.0-1145.155
Upgrade
Upgrade ubuntu/linux-oracle-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1083.89~20.04.1
Upgrade
Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.
Fixed in 5.4.0-1130.143
Upgrade
Upgrade ubuntu/linux-riscv-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1081.85~20.04.1
Upgrade
Upgrade ubuntu/linux-xilinx-zynqmp to a version that resolves this vulnerability.
Fixed in 5.4.0-1065.69
Upgrade
Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.
Fixed in 5.4.0-1147.157+fips1
Upgrade
Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.
Fixed in 5.4.0-1153.160+fips1
Upgrade
Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 5.4.0-1121.131
Upgrade
Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.
Fixed in 5.4.0-1150.159+fips1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 5.15.0-142.152
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 5.15.0-1086.93
Upgrade
Upgrade ubuntu/linux-aws-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1039.41~22.04.1
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 5.15.0-1091.100
Upgrade
Upgrade ubuntu/linux-azure-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1036.42~22.04.1
Upgrade
Upgrade ubuntu/linux-azure-fde to a version that resolves this vulnerability.
Fixed in 5.15.0-1091.100.1
Upgrade
Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 5.15.0-1085.94
Upgrade
Upgrade ubuntu/linux-gcp-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1040.42~22.04.1
Upgrade
Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.
Fixed in 5.15.0-1083.89
Upgrade
Upgrade ubuntu/linux-gkeop to a version that resolves this vulnerability.
Fixed in 5.15.0-1068.76
Upgrade
Upgrade ubuntu/linux-hwe-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-85.85~22.04.1
Upgrade
Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.
Fixed in 5.15.0-1078.81
Upgrade
Upgrade ubuntu/linux-ibm-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1037.37~22.04.1
Upgrade
Upgrade ubuntu/linux-intel-iotg to a version that resolves this vulnerability.
Fixed in 5.15.0-1081.87
Upgrade
Upgrade ubuntu/linux-kvm to a version that resolves this vulnerability.
Fixed in 5.15.0-1082.87
Upgrade
Upgrade ubuntu/linux-lowlatency to a version that resolves this vulnerability.
Fixed in 5.15.0-142.152
Upgrade
Upgrade ubuntu/linux-lowlatency-hwe-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-84.84.1~22.04.1
Upgrade
Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.
Fixed in 5.15.0-1080.81
Upgrade
Upgrade ubuntu/linux-nvidia-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1039.42~22.04.1
Upgrade
Upgrade ubuntu/linux-nvidia-tegra to a version that resolves this vulnerability.
Fixed in 5.15.0-1039.39
Upgrade
Upgrade ubuntu/linux-nvidia-tegra-igx to a version that resolves this vulnerability.
Fixed in 5.15.0-1028.28
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 5.15.0-1083.89
Upgrade
Upgrade ubuntu/linux-oracle-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1037.38~22.04.1
Upgrade
Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.
Fixed in 5.15.0-1080.83
Upgrade
Upgrade ubuntu/linux-riscv-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-84.84~22.04.1
Upgrade
Upgrade ubuntu/linux-xilinx-zynqmp to a version that resolves this vulnerability.
Fixed in 5.15.0-1050.54
Upgrade
Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.
Fixed in 5.15.0-1069.71
Upgrade
Upgrade ubuntu/linux-intel-iot-realtime to a version that resolves this vulnerability.
Fixed in 5.15.0-1079.81
Upgrade
Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.
Fixed in 5.15.0-1086.95
Upgrade
Upgrade ubuntu/linux-realtime-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.1-1034.35~22.04.1
Upgrade
Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-1086.93+fips1
Upgrade
Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-1091.100+fips1
Upgrade
Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-142.152+fips1
Upgrade
Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.
Fixed in 5.15.0-1085.94+fips1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 6.8.0-84.84
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 6.8.0-1039.41
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Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 6.8.0-1038.44
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Fixed in 6.11.0-1018.18~24.04.1
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Fixed in 6.8.0-1025.27
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Fixed in 6.8.0-1040.42
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Fixed in 6.11.0-1016.16~24.04.1
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Fixed in 6.8.0-1036.40
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Fixed in 6.8.0-1023.25
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Fixed in 6.11.0-28.28~24.04.1
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Fixed in 6.8.0-1037.37
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Fixed in 6.8.0-84.84.1
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Fixed in 6.11.0-1015.16~24.04.2
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Fixed in 6.8.0-1039.42
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Fixed in 6.11.0-1012.12
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Fixed in 6.8.0-1039.42.1
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Fixed in 6.8.0-1010.10
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Fixed in 6.11.0-1024.24
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Fixed in 6.8.0-1037.38
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Fixed in 6.8.0-1039.43
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Fixed in 6.8.0-1018.19
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Fixed in 6.8.0-2030.31
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Fixed in 6.8.1-1034.35
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Fixed in 6.8.0-1039.41+fips1
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Fixed in 6.8.0-1040.46+fips1
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Fixed in 6.8.0-84.84+fips1
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Fixed in 6.8.0-1040.42+fips1
Compensating control
In load_microcode_amd(), iterate only over NUMA nodes whose CPU masks are non-empty before determining the first CPU on each node or accessing per-CPU data.

Event History

Apr 2, 2025

CVE Published

via OSV·01:15 PM

Data Sourced

via OSV·01:15 PM

DescriptionSeverityAffected Software

Frequently Asked Questions

Which systems are exposed to the out-of-bounds access?

The affected condition requires an AMD system with CPU-less NUMA nodes, such as a machine using far memory, where a NUMA node has an empty CPU mask. The listed Ubuntu kernel packages include linux, linux-aws, linux-azure, linux-gcp, their relevant FIPS variants, and linux-realtime.

What is required to trigger the issue?

A microcode update must be flashed on the affected AMD system. Flashing microcode is a privileged operation, so an attacker would need privileges sufficient to initiate that operation.

Is this primarily a security exposure or a reliability issue?

The provided information states that it has no security implications because microcode flashing is privileged. The practical concern is reliability: the out-of-bounds per-CPU array access may corrupt memory while applying a microcode update.

How can administrators identify the affected configuration?

Check whether the system is an AMD machine with NUMA nodes that contain memory but no CPUs, resulting in an empty CPU mask for a node. On kernels booted with CONFIG_UBSAN_BOUNDS=y, applying a microcode update can produce an array-index-out-of-bounds UBSAN report in the AMD microcode code.

UBUNTU-CVE-2025-21991: High severity ubuntu/linux-hwe-edge vulnerability

Affected Software

Remediation

Event History

Frequently Asked Questions

Which systems are exposed to the out-of-bounds access?

What is required to trigger the issue?

Is this primarily a security exposure or a reliability issue?

How can administrators identify the affected configuration?

Company

Resources

Contact

Frequently Asked Questions

Which systems are exposed to the out-of-bounds access?

What is required to trigger the issue?

Is this primarily a security exposure or a reliability issue?

How can administrators identify the affected configuration?