CVE-2025-21991
Vulnérabilité élevée dans Linux (Linux)
Description
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. ]
Gravité et risque d'exploitation
CVE-2025-21991 obtient un score CVSS de 7.8/10, soit une gravité élevée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.22 %, ce qui la place devant 11.8 % des CVE référencées.
Que faire ?
- Vérifiez si Linux (versions <d509c4731090ebd9bbdb72c70a2d70003ae81f4f, <=6.1.*, d576547f489c935b9897d4acf8beee3325dea8a5, <=6.12.*, 5.15.180, 7ff6edf4fef38ab404ee7861f257e28eaaeed35f, 6.1.16, 0, <6.1.132, d6353e2fc12c5b8f00f86efa30ed73d2da2f77be, 6.12.20, <e3e89178a9f4a80092578af3ff3c8478f9187d59, 5.10.173, 4.19.276, <6.3, <985a536e04bbfffb1770df43c6470f635a6b1073, 6.14, <4.20, <5.10.236, <=5.10.*, <=6.6.*, 44a44b57e88f311c1415be1f567c50050913c149, 6.13.8, be2710deaed3ab1402379a2ede30a3754fe6767a, <488ffc0cac38f203979f83634236ee53251ce593, 6.1.132, 6.2.3, 6.3, <=5.4.*, 5.15.99, eaf5dea1eb8c2928554b3ca717575cbe232b843c, <5.15.180, 979e197968a1e8f09bf0d706801dba4432f85ab3, 1b1e0eb1d2971a686b9f7bdc146115bcefcbb960, <5.4.292, <e686349cc19e800dac8971929089ba5ff59abfb0, 5.4.235, 5.10.236, <=*, <18b5d857c6496b78ead2fd10001b81ae32d30cac, <=5.15.*, 6.6.84, <5ac295dfccb5b015493f86694fa13a0dde4d3665, <4.15, 5.4.292, <=6.13.*, 4.14.308, <ec52240622c4d218d0240079b7c1d3ec2328a9f4) est présent sur votre parc.
- Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
- À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
- Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.
Références
- https://git.kernel.org/stable/c/d509c4731090ebd9bbdb72c70a2d70003ae81f4f
- https://git.kernel.org/stable/c/985a536e04bbfffb1770df43c6470f635a6b1073
- https://git.kernel.org/stable/c/18b5d857c6496b78ead2fd10001b81ae32d30cac
- https://git.kernel.org/stable/c/ec52240622c4d218d0240079b7c1d3ec2328a9f4
- https://git.kernel.org/stable/c/e686349cc19e800dac8971929089ba5ff59abfb0
- https://git.kernel.org/stable/c/488ffc0cac38f203979f83634236ee53251ce593
- https://git.kernel.org/stable/c/5ac295dfccb5b015493f86694fa13a0dde4d3665
- https://git.kernel.org/stable/c/e3e89178a9f4a80092578af3ff3c8478f9187d59