CVE-2026-72132

A flaw was found in the Linux kernel's Network File System (NFS) component. The nfs_folio_mark_unstable() and nfs_folio_clear_commit() functions incorrectly account for unstable writes, charging the full folio size for each sub-folio request. This inflated accounting can push the system's dirty page threshold, leading to a system-wide throttling of all buffered writers, including unrelated in-kernel NFS server threads. This can result in a denial of service for affected systems.

NFS unstable write accounting can overcharge writeback by the full folio size for every split request instead of the request range size. With large folios and small request splits such as pNFS flexfiles striping or wsize limited splitting, dirty and writeback accounting can be inflated by large factors and can push the host into the hard throttle path for buffered writers. For the CVSS the PR:L is used for the paranoid score because a local user or local process with write access to the affected NFS mount can generate the write workload, while no administrative privilege is normally required for ordinary file writes. The issue is not directly network reachable in the CVSS sense because reliable triggering requires a local writer on an affected NFS client configuration rather than only sending packets to the host. Impact is denial of service through host wide write throttling and degraded write progress, with no evidence of memory corruption or privilege escalation.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.