CVE-2026-72217

Technical Description

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

SUNRPC: Bound-check xdr_buf_to_bvec() stores before writing

xdr_buf_to_bvec() writes a bio_vec into the caller's array before

testing whether that slot is in range, and the head branch performs

the store with no check at all. When the caller's budget is exactly

used up, the next store lands one element past the end of the array.

The overflow label returns count - 1, which masks the surplus store

but cannot undo it.

rq_bvec, the array passed by nfsd_vfs_write(), is allocated to

exactly rq_maxpages entries with no slack. The OOB store can land in

adjacent slab memory; the bv_len and bv_offset fields written there

are derived from client-supplied RPC payload sizes.

Move the in-range check ahead of the store in the head, page-loop,

and tail branches. With the check at the top of each sequence, count

is incremented only after a successful store, so the overflow label

can return count directly.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References