Critical Linux Kernel ksmbd SMB server Out-Of-Bounds Write Scores 9.8 CVSS

Status: UPDATED  |  Advisory ID: CVE-2026-31705

Key Details

Affected Products, Subsystems & Sectors

What to Know

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

ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment

smb2_get_ea() applies 4-byte alignment padding via memset() after

writing each EA entry. The bounds check on buf_free_len is performed

before the value memcpy, but the alignment memset fires unconditionally

afterward with no check on remaining space.

When the EA value exactly fills the remaining buffer (buf_free_len == 0

after value subtraction), the alignment memset writes 1-3 NUL bytes

past the buf_free_len boundary. In compound requests where the response

buffer is shared across commands, the first command (e.g., READ) can

consume most of the buffer, leaving a tight remainder for the QUERY_INFO

EA response. The alignment memset then overwrites past the physical

kvmalloc allocation into adjacent kernel heap memory.

Add a bounds check before the alignment memset to ensure buf_free_len

can accommodate the padding bytes.

This is the same bug pattern fixed by commit beef2634f81f ("ksmbd: fix

potencial OOB in get_file_all_info() for compound requests") and

commit fda9522ed6af ("ksmbd: fix OOB write in QUERY_INFO for compound

requests"), both of which added bounds checks before unconditional

writes in QUERY_INFO response handlers. (NVD)

What to Do

Monitor Linux's and Siemens's web pages for any future patch releases.

References