CVE-2025-21991

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Source
https://cve.org/CVERecord?id=CVE-2025-21991
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-21991.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2025-21991
Downstream
AZL (2)
BELL (1)
CLSA (3)
DEBIAN (1)
ECHO (1)
MGASA (2)
MINI (1)
OESA (3)
RHSA (9)
RLSA (4)
ROOT (1)
SUSE (10)
UBUNTU (1)
Related
ALSA (4)
SUSE (10)
Published
2025-04-02T12:53:14Z
Modified
2026-10-20T10:30:21Z
Severity
  • 7.8 (High) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H CVSS Calculator
Summary
x86/microcode/AMD: Fix out-of-bounds on systems with CPU-less NUMA nodes
Details

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, load_microcode_amd() 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):

  • cpumask_of_node(nid) is 0
  • cpumask_first(0) is CONFIG_NR_CPUS
  • cpu_data(CONFIG_NR_CPUS) accesses the cpu_info 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 CONFIG_UBSAN_BOUNDS=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: dump_stack __ubsan_handle_out_of_bounds load_microcode_amd request_microcode_amd reload_store kernfs_fop_write_iter vfs_write ksys_write do_syscall_64 entry_SYSCALL_64_after_hwframe

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. ]

Database specific 
{
    "cna_assigner":  "Linux",
    "osv_generated_from":  "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21991.json"
}
References

Affected packages

Git / git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git

Affected ranges

Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
979e197968a1e8f09bf0d706801dba4432f85ab3
Fixed
d509c4731090ebd9bbdb72c70a2d70003ae81f4f
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
44a44b57e88f311c1415be1f567c50050913c149
Fixed
985a536e04bbfffb1770df43c6470f635a6b1073
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
be2710deaed3ab1402379a2ede30a3754fe6767a
Fixed
18b5d857c6496b78ead2fd10001b81ae32d30cac
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
d576547f489c935b9897d4acf8beee3325dea8a5
Fixed
ec52240622c4d218d0240079b7c1d3ec2328a9f4
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
7ff6edf4fef38ab404ee7861f257e28eaaeed35f
Fixed
e686349cc19e800dac8971929089ba5ff59abfb0
Fixed
488ffc0cac38f203979f83634236ee53251ce593
Fixed
5ac295dfccb5b015493f86694fa13a0dde4d3665
Fixed
e3e89178a9f4a80092578af3ff3c8478f9187d59
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
5.4.235
Fixed
5.4.292
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
5.10.173
Fixed
5.10.236
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
5.15.99
Fixed
5.15.180
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
6.1.16
Fixed
6.1.132
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
4.14.308
Fixed
4.15
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
4.19.276
Fixed
4.20
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
6.2.3
Fixed
6.3
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
d6353e2fc12c5b8f00f86efa30ed73d2da2f77be
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
1b1e0eb1d2971a686b9f7bdc146115bcefcbb960
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
eaf5dea1eb8c2928554b3ca717575cbe232b843c

Affected versions

v4.*
v4.14.308
v4.14.309
v4.14.310
v4.14.311
v4.14.312
v4.14.313
v4.14.314
v4.14.315
v4.14.316
v4.14.317
v4.14.318
v4.14.319
v4.14.320
v4.14.321
v4.14.322
v4.14.323
v4.14.324
v4.14.325
v4.14.326
v4.14.327
v4.14.328
v4.14.329
v4.14.330
v4.14.331
v4.14.332
v4.14.333
v4.14.334
v4.14.335
v4.14.336
v4.19.276
v4.19.277
v4.19.278
v4.19.279
v4.19.280
v4.19.281
v4.19.282
v4.19.283
v4.19.284
v4.19.285
v4.19.286
v4.19.287
v4.19.288
v4.19.289
v4.19.290
v4.19.291
v4.19.292
v4.19.293
v4.19.294
v4.19.295
v4.19.296
v4.19.297
v4.19.298
v4.19.299
v4.19.300
v4.19.301
v4.19.302
v4.19.303
v4.19.304
v4.19.305
v4.19.306
v4.19.307
v4.19.308
v4.19.309
v4.19.310
v4.19.311
v4.19.312
v4.19.313
v4.19.314
v4.19.315
v4.19.316
v4.19.317
v4.19.318
v4.19.319
v4.19.320
v4.19.321
v4.19.322
v4.19.323
v4.19.324
v4.19.325
v5.*
v5.10.173
v5.10.174
v5.10.175
v5.10.176
v5.10.177
v5.10.178
v5.10.179
v5.10.180
v5.10.181
v5.10.182
v5.10.183
v5.10.184
v5.10.185
v5.10.186
v5.10.187
v5.10.188
v5.10.189
v5.10.190
v5.10.191
v5.10.192
v5.10.193
v5.10.194
v5.10.195
v5.10.196
v5.10.197
v5.10.198
v5.10.199
v5.10.200
v5.10.201
v5.10.202
v5.10.203
v5.10.204
v5.10.205
v5.10.206
v5.10.207
v5.10.208
v5.10.209
v5.10.210
v5.10.211
v5.10.212
v5.10.213
v5.10.214
v5.10.215
v5.10.216
v5.10.217
v5.10.218
v5.10.219
v5.10.220
v5.10.221
v5.10.222
v5.10.223
v5.10.224
v5.10.225
v5.10.226
v5.10.227
v5.10.228
v5.10.229
v5.10.230
v5.10.231
v5.10.232
v5.10.233
v5.10.234
v5.10.235
v5.15.100
v5.15.101
v5.15.102
v5.15.103
v5.15.104
v5.15.105
v5.15.106
v5.15.107
v5.15.108
v5.15.109
v5.15.110
v5.15.111
v5.15.112
v5.15.113
v5.15.114
v5.15.115
v5.15.116
v5.15.117
v5.15.118
v5.15.119
v5.15.120
v5.15.121
v5.15.122
v5.15.123
v5.15.124
v5.15.125
v5.15.126
v5.15.127
v5.15.128
v5.15.129
v5.15.130
v5.15.131
v5.15.132
v5.15.133
v5.15.134
v5.15.135
v5.15.136
v5.15.137
v5.15.138
v5.15.139
v5.15.140
v5.15.141
v5.15.142
v5.15.143
v5.15.144
v5.15.145
v5.15.146
v5.15.147
v5.15.148
v5.15.149
v5.15.150
v5.15.151
v5.15.152
v5.15.153
v5.15.154
v5.15.155
v5.15.156
v5.15.157
v5.15.158
v5.15.159
v5.15.160
v5.15.161
v5.15.162
v5.15.163
v5.15.164
v5.15.165
v5.15.166
v5.15.167
v5.15.168
v5.15.169
v5.15.170
v5.15.171
v5.15.172
v5.15.173
v5.15.174
v5.15.175
v5.15.176
v5.15.177
v5.15.178
v5.15.179
v5.15.99
v5.4.235
v5.4.236
v5.4.237
v5.4.238
v5.4.239
v5.4.240
v5.4.241
v5.4.242
v5.4.243
v5.4.244
v5.4.245
v5.4.246
v5.4.247
v5.4.248
v5.4.249
v5.4.250
v5.4.251
v5.4.252
v5.4.253
v5.4.254
v5.4.255
v5.4.256
v5.4.257
v5.4.258
v5.4.259
v5.4.260
v5.4.261
v5.4.262
v5.4.263
v5.4.264
v5.4.265
v5.4.266
v5.4.267
v5.4.268
v5.4.269
v5.4.270
v5.4.271
v5.4.272
v5.4.273
v5.4.274
v5.4.275
v5.4.276
v5.4.277
v5.4.278
v5.4.279
v5.4.280
v5.4.281
v5.4.282
v5.4.283
v5.4.284
v5.4.285
v5.4.286
v5.4.287
v5.4.288
v5.4.289
v5.4.290
v5.4.291
v6.*
v6.1.100
v6.1.101
v6.1.102
v6.1.103
v6.1.104
v6.1.105
v6.1.106
v6.1.107
v6.1.108
v6.1.109
v6.1.110
v6.1.111
v6.1.112
v6.1.113
v6.1.114
v6.1.115
v6.1.116
v6.1.117
v6.1.118
v6.1.119
v6.1.120
v6.1.121
v6.1.122
v6.1.123
v6.1.124
v6.1.125
v6.1.126
v6.1.127
v6.1.128
v6.1.129
v6.1.130
v6.1.131
v6.1.16
v6.1.17
v6.1.18
v6.1.19
v6.1.20
v6.1.21
v6.1.22
v6.1.23
v6.1.24
v6.1.25
v6.1.26
v6.1.27
v6.1.28
v6.1.29
v6.1.30
v6.1.31
v6.1.32
v6.1.33
v6.1.34
v6.1.35
v6.1.36
v6.1.37
v6.1.38
v6.1.39
v6.1.40
v6.1.41
v6.1.42
v6.1.43
v6.1.44
v6.1.45
v6.1.46
v6.1.47
v6.1.48
v6.1.49
v6.1.50
v6.1.51
v6.1.52
v6.1.53
v6.1.54
v6.1.55
v6.1.56
v6.1.57
v6.1.58
v6.1.59
v6.1.60
v6.1.61
v6.1.62
v6.1.63
v6.1.64
v6.1.65
v6.1.66
v6.1.67
v6.1.68
v6.1.69
v6.1.70
v6.1.71
v6.1.72
v6.1.73
v6.1.74
v6.1.75
v6.1.76
v6.1.77
v6.1.78
v6.1.79
v6.1.80
v6.1.81
v6.1.82
v6.1.83
v6.1.84
v6.1.85
v6.1.86
v6.1.87
v6.1.88
v6.1.89
v6.1.90
v6.1.91
v6.1.92
v6.1.93
v6.1.94
v6.1.95
v6.1.96
v6.1.97
v6.1.98
v6.1.99
v6.2.10
v6.2.11
v6.2.12
v6.2.13
v6.2.14
v6.2.15
v6.2.16
v6.2.3
v6.2.4
v6.2.5
v6.2.6
v6.2.7
v6.2.8
v6.2.9

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-21991.json"

Linux / Kernel

Package

Name
Kernel

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected
Fixed
5.4.292
Type
ECOSYSTEM
Events
Introduced
5.5.0
Fixed
5.10.236
Type
ECOSYSTEM
Events
Introduced
5.11.0
Fixed
5.15.180
Type
ECOSYSTEM
Events
Introduced
5.16.0
Fixed
6.1.132
Type
ECOSYSTEM
Events
Introduced
6.2.0
Fixed
6.6.84
Type
ECOSYSTEM
Events
Introduced
6.3.0
Fixed
6.12.20
Type
ECOSYSTEM
Events
Introduced
6.7.0
Fixed
6.13.8

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-21991.json"