CVE-2026-98116

Description

In the Linux kernel, the following vulnerability has been resolved: ALSA: pcm: Serialize PCM mmap with buffer reallocation to fix page UAF snd_pcm_hw_params() and snd_pcm_hw_free() guard buffer reallocation with an mmap_count check performed under the PCM stream lock, but the lock is released long before the buffer is actually freed: snd_pcm_sync_stop(), constraint refinement and do_free_pages() all happen in between. snd_pcm_mmap_data(), on the other hand, takes no lock at all: it validates against the old buffer's state and dma_bytes, remaps its pages into the VMA, and only then increments mmap_count. A concurrent mmap() can therefore slip in between the check and the free. remap_pfn_range() installs writable PTEs for the old buffer's pages without taking page references, and the subsequent do_free_pages() returns those pages to the page allocator while the VMA still maps them. This leaves a stale, writable mapping of freed pages: a page-level use-after-free that can be leveraged for local privilege escalation. Make snd_pcm_mmap_data() participate in the buffer-access scheme introduced for hw_params/hw_free: acquire runtime->buffer_accessing before validating and remapping, and release it afterwards. Buffer reallocation already fails with -EBUSY while accessors are active, and the mmap side now fails with -EBUSY while a reallocation is in progress, so the validate/remap sequence and the check/free sequence can no longer interleave. A reproducer that turns this race into a stale writable mapping of the freed DMA buffer pages is available on request.

Gravité et risque d'exploitation

CVE-2026-98116 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 0.13 %, ce qui la place devant 2.1 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <5.11, <=6.1.*, <e6cdd2a0470d64073349a970dc1691433804b271, <=6.12.*, 7.2.7, 5.18, 92ee3c60ec9fe64404dc035e7c41277d74aa26cb, <9857a75714bb5df4781e4d8b1a1753b1e17bf07a, <9b110a9dcecc59516c77cb3c0caf1f492f75df2d, 0090c13cbbdffd7da079ac56f80373a9a1be0bf8, 6.18.53, <fd137bf8149bc6460f9b7b1fc292025da04cb9ee, 0, 5.17.1, a42aa926843acca96c0dfbde2e835b8137f2f092, <5.17, 33061d0fba51d2bf70a2ef9645f703c33fe8e438, 9cb6c40a6ebe4a0cfc9d6a181958211682cffea9, 4.19.243, <5.18, <8c1882dfee8f404d118020664b73eb4592172226, <4.20, 6.6.158, 5.4.193, <=6.6.*, 5.15.32, 6.1.189, <cbc7ec97601d09b74e05e44470fa6b0bcdabf3f5, fbeb492694ce0441053de57699e1e2b7bc148a69, 1bbf82d9f961414d6c76a08f7f843ea068e0ab7b, <5.15.222, 0f6947f5f5208f6ebd4d76a82a4757e2839a23f8, <5.5, <=6.18.*, 5.15.222, <cbadf2575d25e7dcc0d4da2717817ae569fbc99b, <=7.2.*, 5.10.109, 4.14.279, <=*, <=5.15.*, <4.15, 5.16.18, 6.12.111, 7.3) 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/e6cdd2a0470d64073349a970dc1691433804b271
• https://git.kernel.org/stable/c/9857a75714bb5df4781e4d8b1a1753b1e17bf07a
• https://git.kernel.org/stable/c/cbadf2575d25e7dcc0d4da2717817ae569fbc99b
• https://git.kernel.org/stable/c/cbc7ec97601d09b74e05e44470fa6b0bcdabf3f5
• https://git.kernel.org/stable/c/fd137bf8149bc6460f9b7b1fc292025da04cb9ee
• https://git.kernel.org/stable/c/8c1882dfee8f404d118020664b73eb4592172226
• https://git.kernel.org/stable/c/9b110a9dcecc59516c77cb3c0caf1f492f75df2d