How severe is CVE-2026-31708?

CVE-2026-31708 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity none, and availability high.

Is CVE-2026-31708 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-31708?

CVE-2026-31708 affects Linux Linux Kernel. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-31708?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-31708 have an EU (EUVD) identifier?

Yes. CVE-2026-31708 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-26517.

When was CVE-2026-31708 published?

CVE-2026-31708 was published on 2026-05-01 and last updated on 2026-06-19.

CVE-2026-31708

CVE-2026-31708 is a high-severity vulnerability in Linux Linux Kernel with a CVSS 3.x base score of 8.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-125.

Key facts

Severity: High (CVSS 3.x base score 8.1)
EPSS exploit prediction: 0% (22nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-26517
Weakness: CWE-125
Affected product: Linux Linux Kernel
Published: 2026-05-01
Last modified: 2026-06-19

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.

Frequently asked questions

What is CVE-2026-31708?: 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.
How severe is CVE-2026-31708?: CVE-2026-31708 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity none, and availability high.
Is CVE-2026-31708 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-31708?: CVE-2026-31708 affects Linux Linux Kernel. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-31708?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-31708 have an EU (EUVD) identifier?: Yes. CVE-2026-31708 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-26517.
When was CVE-2026-31708 published?: CVE-2026-31708 was published on 2026-05-01 and last updated on 2026-06-19.

References

Affected products (1)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

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