CVE-2026-90042
Vulnérabilité critique dans Linux (Linux)
Description
In the Linux kernel, the following vulnerability has been resolved: ceph: properly decrypt filenames in vmalloc() buffers The fscrypt subsystem uses the scatterlist crypto API, inheriting its requirement that any buffers are in the linear mapping region. However, the messenger client uses kvmalloc() to create buffers for messages, which will occasionally place those buffers in the vmalloc() region when physical memory fragmentation doesn't permit a large enough kmalloc(). The various callers of ceph_fname_to_usr() directly pass (slices of) raw messages from the MDS without considering that the messages may be in vmalloc() buffers, resulting in oopses especially on non-x86 platforms (see 'Closes:' for more details and a reproducer). Make ceph_fname_to_usr() explicitly tolerant of vmalloc()-allocated fname->ctext, fname->name, and/or oname->name buffers, using `tname` (which, when non-null, must be a linear address; when null, is briefly allocated as necessary) as a bounce buffer to avoid passing any inappropriate addresses to fscrypt_fname_disk_to_usr(). Additionally change parse_reply_info_readdir() -- the only function to supply its own `tname` -- to follow the new "tname must never come from vmalloc()" rule by passing NULL when the message is not in the linear region. Though this causes a per-dentry kmalloc()+kfree(), this overhead exists only when processing the minority of messages that spill into vmalloc(). My (crude) testing puts this at only about 1 in 8,000 readdir messages. Still, if the overhead proves unreasonable in the future, it is easy enough to mitigate: a future change could allocate a bounce buffer in parse_reply_info_readdir() and use that as `tname` instead.
Gravité et risque d'exploitation
CVE-2026-90042 obtient un score CVSS de 9.8/10, soit une gravité critique. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.50 %, ce qui la place devant 41.7 % des CVE référencées.
Que faire ?
- Vérifiez si Linux (versions <93729594af506557a86f8b603be7ac5f3370eeca, 6.18.51, 6.6, <3b467c68803d7c7e82678289e598afd44faa6101, <=6.12.*, <=*, <110747ff535e3d98ac17d68dbd056bb6ef000e23, <6.6, <=7.2.*, <=6.18.*, 0, 457117f077c6749d1e28469eae91fb69c9806768, 7.2.5, 6.12.111, <e939fc6a7bd969a58a150b7f188c1047138403e3, 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.