PT-2026-44230 · Linux · Linux

Published 2026-05-28 · Updated 2026-05-28 · CVE-2026-46107

NVD

CVSS v3.1

7.8

High

Base vector

AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

In the Linux kernel, the following vulnerability has been resolved:

dm-thin: fix metadata refcount underflow

There's a bug in dm-thin in the function rebalance children. If the internal btree node has one entry, the code tries to copy all btree entries from the node's child to the node itself and then decrement the child's reference count.

If the child node is shared (it has reference count > 1), we won't free it, so there would be two pointers to each of the grandchildren nodes. But the reference counts of the grandchildren is not increased, thus the reference count doesn't match the number of pointers that point to the grandchildren. This results in "device mapper: space map common: unable to decrement block" errors.

Fix this bug by incrementing reference counts on the grandchildren if the btree node is shared.

Fix

Related Identifiers

CVE-2026-46107

Affected Products

Linux

References · 6

• https://nvd.nist.gov/vuln/detail/CVE-2026-46107 · Security Note
• https://git.kernel.org/stable/c/09a65adc7d8bbfce06392cb6d375468e2728ead5 · Note
• https://git.kernel.org/stable/c/85311a585a26640760cd0f3349ab9f2905691044 · Note
• https://git.kernel.org/stable/c/5ec0debbcfd43596e32c1239e993de06a704e04c · Note
• https://git.kernel.org/stable/c/323d252a4a378834e4fe68298ca61cfc5dd3a460 · Note
• https://git.kernel.org/stable/c/12161e03d33afce781f68fa11cc6060538862fad · Note