CVE-2026-89633

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

smb: client: fix OOB read/write from unvalidated DataOffset in coalesce t2()

coalesce t2() computes data pointers directly from server-supplied DataOffset fields with no validation against buffer bounds:

data area of tgt = (char *)&pSMBt->hdr.Protocol + get unaligned le16(&pSMBt->t2 rsp.DataOffset); data area of src = (char *)&pSMBs->hdr.Protocol + get unaligned le16(&pSMBs->t2 rsp.DataOffset); data area of tgt += total in tgt; ... memcpy(data area of tgt, data area of src, total in src);

A small DataOffset can push a pointer below the actual byte area, overwriting header fields; a large one can push it past the buffer end, causing out-of-bounds heap reads (source) or writes (target). The BCC overflow guard does not prevent this: BCC reflects how much data is present, while DataOffset controls where in the buffer it starts.

The "validate target area" comment present since the function was first written in 2005 was a placeholder that was never implemented.

Add lower- and upper-bound checks for both data pointers before the memcpy, and before any target header fields are modified.