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.

A flaw was found in the Linux kernel's Device Mapper (dm-thin) component. This vulnerability, a metadata reference count underflow, occurs in the `rebalance_children` function. When an internal btree node with a single entry is shared, the system incorrectly tracks the usage of child nodes. This can lead to 'device mapper: space map common: unable to decrement block' errors, potentially causing a denial of service or data integrity issues.

Red Hat Enterprise Linux 10 Fix deferred kernel Red Hat Enterprise Linux 6 Out of support scope kernel Red Hat Enterprise Linux 7 Fix deferred kernel Red Hat Enterprise Linux 7 Fix deferred kernel-rt Red Hat Enterprise Linux 8 Fix deferred kernel Red Hat Enterprise Linux 8 Fix deferred kernel-rt Red Hat Enterprise Linux 9 Fix deferred kernel Red Hat Enterprise Linux 9 Fix deferred kernel-rt https://www.cve.org/CVERecord?id=CVE-2026-46107 https://nvd.nist.gov/vuln/detail/CVE-2026-46107 https://lore.kernel.org/linux-cve-announce/2026052812-CVE-2026-46107-709a@gregkh/T