CVE-2026-98126

A flaw was found in the Linux kernel's SMB client. This flaw allows a local user to bypass enforced file-size restrictions and expand files beyond authorized limits. When handling file allocation operations that zero out a range of data without preserving the file's existing size, the kernel fails to check whether the new size exceeds configured process file-size limits (RLIMIT_FSIZE). Consequently, a local user can write or extend files on mounted network shares beyond permitted resource boundaries.

A low impact flaw was found in the Linux kernel SMB client, affecting the kernel as shipped in Red Hat Enterprise Linux 8, 9, and 10, Red Hat In-Vehicle OS 2, and the RHEL CoreOS 8 and 9 kernels used in OpenShift Container Platform 4. When the fallocate() operation FALLOC_FL_ZERO_RANGE is used without FALLOC_FL_KEEP_SIZE on a file stored on a CIFS/SMB mount, smb3_zero_range() may extend the file beyond EOF without first checking the caller's RLIMIT_FSIZE limit. This allows a local user with write access to a file on the mounted share to grow that file beyond the file-size limit configured for their process. The consequence is a local resource-policy bypass with no direct confidentiality or integrity impact: the caller already has write access to the target file, and the main effect is potential storage consumption beyond the intended per-process boundary. Although the CVSS:3.1 base score is 5.5 (Moderate), Red Hat rates the overall impact as Low because exploitation requires local access and write permission on the target file, and the issue is limited to bypassing a per-process resource limit. Red Hat Enterprise Linux 6 and 7 are not affected because the vulnerable code is not present in those streams. Given the low impact, fixes for the affected products are currently deferred to future maintenance updates rather than delivered as immediate updates; the residual risk until a fix is delivered is limited to a local user exceeding file-size limits on SMB-mounted files, which server-side quotas and available-space limits can further constrain.

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 do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.