CVE-2026-31708

High

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.

Package Linux Kernel
Published 2026-05-01
Last modified 2026-06-01
CVSS version 3.1
Patch available
Yes

CVSS 3.1 score

8.1

out of 10
High
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H

Weakness type

CWE-125

CVE-2026-31708 is a Out-of-bounds Read vulnerability

What is Out-of-bounds Read?

The product reads data past the end or before the beginning of the intended buffer. Learn more on MITRE CWE

Affected versions

Linux kernel versions 5.1 and later are affected. Fixed in 6.1.175, 6.6.136, 6.12.84, 6.18.25, 7.0.2, 7.1-rc1 and their respective stable series.

Affected from
≥ 5.1
Fixed in
✓ 6.1.175 6.1.x ✓ 6.6.136 6.6.x ✓ 6.12.84 6.12.x ✓ 6.18.25 6.18.x ✓ 7.0.2 7.0.x ✓ 7.1-rc1

References

The following references provide additional information about CVE-2026-31708 including vendor advisories, patch commits, exploit details, and third-party analysis. Links are sourced from the NIST NVD database.

6 patch commits total View all on NVD

Frequently asked questions

  • What is CVE-2026-31708?

    CVE-2026-31708 is a High severity Linux kernel vulnerability with a CVSS score of 8.1 out of 10 , classified as an Out-of-bounds Read flaw (CWE-125) . It affects Linux kernel versions from 5.1 onward and has been patched in 6.1.175, 6.6.136, 6.12.84 and others. CVE-2026-31708 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2026-31708?

    CVE-2026-31708 has a CVSS score of 8.1 out of 10, rated High severity (CVSS 3.1). The vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H .

  • Is there a patch available for CVE-2026-31708?

    Yes — CVE-2026-31708 has been patched. Fixed versions include 6.1.175, 6.6.136, 6.12.84 and others. If you are running Linux kernel 5.1 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2026-31708 actively exploited?

    No — CVE-2026-31708 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

  • What is Out-of-bounds Read (CWE-125)?

    The product reads data past the end or before the beginning of the intended buffer. View CWE-125 on MITRE CWE →

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