CVE-2026-31433 ksmbd: fix potencial OOB in get_file_all_info() for compound requests
A missing buffer length check in the Linux kernel ksmbd module allows out-of-bounds writes during compound SMB requests, potentially leading to memory corruption or crashes.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-31433?
CVE-2026-31433 is a high-severity memory corruption vulnerability in Linux kernel, published on 22 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: fix potencial OOB in get_file_all_info() for compound requests
When a compound request consists of QUERY_DIRECTORY + QUERY_INFO (FILE_ALL_INFORMATION) and the first command consumes nearly the entire max_trans_size, get_file_all_info() would blindly call smbConvertToUTF16() with PATH_MAX, causing out-of-bounds write beyond the response buffer. In get_file_all_info(), there was a missing validation check for the client-provided OutputBufferLength before copying the filename into FileName field of the smb2_file_all_info structure. If the filename length exceeds the available buffer space, it could lead to potential buffer overflows or memory corruption during smbConvertToUTF16 conversion. This calculating the actual free buffer size using smb2_calc_max_out_buf_len() and returning -EINVAL if the buffer is insufficient and updating smbConvertToUTF16 to use the actual filename length (clamped by PATH_MAX) to ensure a safe copy operation.
Weakness: CWE-125
Which versions are affected by CVE-2026-31433?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-31433?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-31433 being exploited?
There is no known exploitation of CVE-2026-31433 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-31433, DEBIAN-CVE-2026-31433, GHSA-32xq-pcg8-hc33, ROOT-OS-DEBIAN-12-CVE-2026-31433, ROOT-OS-UBUNTU-2204-CVE-2026-31433, ROOT-OS-UBUNTU-2404-CVE-2026-31433 and 1 more.