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CVE-2026-90042 Affecting linux-6.12 package, versions <6.12.111-1~deb12u1

Severity

 Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.67% (50th percentile)

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  • Snyk IDSNYK-DEBIAN12-LINUX612-20506690
  • published5 Oct 2026
  • disclosed16 Sept 2026
Report a new vulnerability Found a mistake?

Introduced: 16 Sep 2026

NewCVE-2026-90042  (opens in a new tab)

How to fix?

Upgrade Debian:12 linux-6.12 to version 6.12.111-1~deb12u1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream linux-6.12 package and not the linux-6.12 package as distributed by Debian. See How to fix? for Debian:12 relevant fixed versions and status.

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.