High severity · published May 1, 2026
CVE-2026-31708
smb: client: fix OOB read in smb2_ioctl_query_info QUERY_INFO path
8.1
CVSS
0.4%
EPSS
No
On KEV
Description
In the Linux kernel, the following vulnerability has been resolved: smb: client: fix OOB read in smb2_ioctl_query_info QUERY_INFO path smb2_ioctl_query_info() has two response-copy branches: PASSTHRU_FSCTL and the default QUERY_INFO path. The QUERY_INFO branch clamps qi.input_buffer_length to the server-reported OutputBufferLength and then copies qi.input_buffer_length bytes from qi_rsp->Buffer to userspace, but it never verifies that the flexible-array payload actually fits within rsp_iov[1].iov_len. A malicious server can return OutputBufferLength larger than the actual QUERY_INFO response, causing copy_to_user() to walk past the response buffer and expose adjacent kernel heap to userspace. Guard the QUERY_INFO copy with a bounds check on the actual Buffer payload. Use struct_size(qi_rsp, Buffer, qi.input_buffer_length) rather than an open-coded addition so the guard cannot overflow on 32-bit builds.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
High
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 29% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
KE
Kernel · Linux
5.1 before 6.6.136; 6.7 before 6.12.84; 6.13 before 6.18.25; 6.19 before 7.0.2 · source: NVD
LI
Linux · Linux
f5778c398713692a16150ae96e5c8270bab8399f before e66bdc0704977ecee667a81d38255b579c2353d0; f5778c398713692a16150ae96e5c8270bab8399f before 9e203dbb5402897c43130fb171a2617008a91f45; f5778c398713692a16150ae96e5c8270bab8399f before 1dd757379997b71a328a4b591ffaf481acd0ead1; f5778c398713692a16150ae96e5c8270bab8399f before a34d456934fe42e4da5d2cc07787bf418bee99c6; f5778c398713692a16150ae96e5c8270bab8399f before ac2f14e4705d020f04e806efa0d49ab8dc2b145f; f5778c398713692a16150ae96e5c8270bab8399f before 078fae8f50adebb903ccf2252b44391324571e78; +3 more · source: vendor