The Linux kernel has a documented integer underflow in the XFS filesystem subsystem, specifically when reserving space for metadata btree files. If the free block count that can be reserved falls below the amount already used, the code subtracts hidden_space without boundary checks, potentially allowing the free block counter to underflow and become a very large negative number. This incorrect accounting can lead to kernel crashes or filesystem corruption, resulting in a denial‑of‑service condition for applications that rely on the affected filesystem.

The bug exists in any Linux kernel that implements the XFS filesystem; the implicated routines are part of the core kernel code. No specific kernel versions or patch levels are identified, so all kernel variants that include the XFS metafile_resv_init function are considered potentially vulnerable.

The flaw is an integer underflow (CWE‑191) and carries a CVSS score of 4.4, indicating moderate severity. The EPSS score of less than 1 % shows a very low expected exploitation probability, and the vulnerability is not yet listed in the CISA KEV catalog. The attack vector is not explicitly disclosed, but it is inferred that local or privileged operations that manipulate XFS metadata are required to trigger the overflow, making remote exploitation unlikely without additional privileges.