CVE-2025-40300

Description

In the Linux kernel, the following vulnerability has been resolved: x86/vmscape: Add conditional IBPB mitigation VMSCAPE is a vulnerability that exploits insufficient branch predictor isolation between a guest and a userspace hypervisor (like QEMU). Existing mitigations already protect kernel/KVM from a malicious guest. Userspace can additionally be protected by flushing the branch predictors after a VMexit. Since it is the userspace that consumes the poisoned branch predictors, conditionally issue an IBPB after a VMexit and before returning to userspace. Workloads that frequently switch between hypervisor and userspace will incur the most overhead from the new IBPB. This new IBPB is not integrated with the existing IBPB sites. For instance, a task can use the existing speculation control prctl() to get an IBPB at context switch time. With this implementation, the IBPB is doubled up: one at context switch and another before running userspace. The intent is to integrate and optimize these cases post-embargo. [ dhansen: elaborate on suboptimal IBPB solution ]

Gravité et risque d'exploitation

CVE-2025-40300 obtient un score CVSS de 0.0/10, soit une gravité non évaluée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.35 %, ce qui la place devant 27.3 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <=6.1.*, <=6.12.*, <=6.16.*, <4.16, <459274c77b37ac63b78c928b4b4e748d1f9d05c8, 6.6.106, 6.17, <15006289e5c38b2a830e1fba221977a27598176c, 0, 5.15.193, <2f8f173413f1cbf52660d04df92d0069c4306d25, <2f4f2f8f860cb4c3336a7435ebe8dcfded0c9c6e, <d5490dfa35427a2967e00a4c7a1b95fdbc8ede34, 5.10.244, 3.16.57, <=5.10.*, <=6.6.*, 6.16.7, 6.12.47, <4.5, 4.4.168, <c08192b5d6730a914dee6175bc71092ee6a65f14, <f866eef8d1c65504d30923c3f14082ad294d0e6d, c51f1e5f57cca88d8d5894b6fad1638f643a99d0, <34e5667041050711a947e260fc9ebebe08bddee5, 6.1.152, <510603f504796c3535f67f55fb0b124a303b44c8, 4.16, <d7ddc93392e4a7ffcccc86edf6ef3e64c778db52, <=*, <893387c18612bb452336a5881da0d015a7e8f4a2, <=5.15.*, <9c23a90648e831d611152ac08dbcd1283d405e7f, <3.17, 15d45071523d89b3fb7372e2135fbd72f6af9506, <ac60717f9a8d21c58617d0b34274babf24135835, 4b3870c343a82cd2df7192cc5149c87205dcc611) 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/ac60717f9a8d21c58617d0b34274babf24135835
• https://git.kernel.org/stable/c/c08192b5d6730a914dee6175bc71092ee6a65f14
• https://git.kernel.org/stable/c/d5490dfa35427a2967e00a4c7a1b95fdbc8ede34
• https://git.kernel.org/stable/c/2f4f2f8f860cb4c3336a7435ebe8dcfded0c9c6e
• https://git.kernel.org/stable/c/15006289e5c38b2a830e1fba221977a27598176c
• https://git.kernel.org/stable/c/893387c18612bb452336a5881da0d015a7e8f4a2
• https://git.kernel.org/stable/c/f866eef8d1c65504d30923c3f14082ad294d0e6d
• https://git.kernel.org/stable/c/34e5667041050711a947e260fc9ebebe08bddee5
• https://git.kernel.org/stable/c/d7ddc93392e4a7ffcccc86edf6ef3e64c778db52
• https://git.kernel.org/stable/c/459274c77b37ac63b78c928b4b4e748d1f9d05c8
• https://git.kernel.org/stable/c/510603f504796c3535f67f55fb0b124a303b44c8
• https://git.kernel.org/stable/c/9c23a90648e831d611152ac08dbcd1283d405e7f
• https://git.kernel.org/stable/c/2f8f173413f1cbf52660d04df92d0069c4306d25