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CVE-2026-90042: Linux

Severity

9.8 (CRITICAL)

Vendor

LINUX

Affected versions

457117f077c6749d1e28469eae91fb69c9806768 through before 110747ff535e3d98ac17d68dbd056bb6ef000e23; 457117f077c6749d1e2846

Patch status

Patched

Published

2026-09-16T11:17:17.450

Modified

2026-09-16T15:18:26.873

Why it matters

Critical vulnerability requiring immediate validation against your environment.

Recommended admin actions

• Prioritize validation immediately due to critical CVSS severity.

Technical summary

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.

View the official NVD record for CVE-2026-90042

CVE data is sourced from NVD/CNA records and optional enrichment. Validate against the vendor advisory before taking production action.