CVE-2026-31708Network attack vector

Kernel heap disclosure via truncated QUERY_INFO response

Published May 1, 2026 · Updated May 1, 2026

Out-of-bounds read in the Linux kernel SMB client allows remote attackers to disclose kernel heap data through a crafted QUERY_INFO response. smb2_ioctl_query_info() trusts the server-reported OutputBufferLength and copies that many bytes from qi_rsp->Buffer without confirming that the flexible-array payload fits within rsp_iov[1].iov_len. Exploitation requires a client request to a malicious SMB server and exposes adjacent kernel heap data to the requesting userspace process.

CVSS severity8.1
High
EPSS probability0.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in the Linux kernel SMB client allows remote attackers to disclose kernel heap data through a crafted QUERY_INFO response. smb2_ioctl_query_info() trusts the server-reported OutputBufferLength and copies that many bytes from qi_rsp->Buffer without confirming that the flexible-array payload fits within rsp_iov[1].iov_len. Exploitation requires a client request to a malicious SMB server and exposes adjacent kernel heap data to the requesting userspace process.

The record

CVE
CVE-2026-31708
Published
May 1, 2026
Updated
May 1, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-125
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 1, 2026CVE publishedPublication date reported by the CVE source.
  2. May 1, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.1
  2. Affected versionversion=f5778c398713692a16150ae96e5c8270bab8399f <078fae8f50adebb903ccf2252b44391324571e78
  3. Affected versionversion=f5778c398713692a16150ae96e5c8270bab8399f <85fd46ee26a11841c670449508025965f61ce131
  4. Affected versionversion=f5778c398713692a16150ae96e5c8270bab8399f <a34d456934fe42e4da5d2cc07787bf418bee99c6
  5. Affected versionversion=f5778c398713692a16150ae96e5c8270bab8399f <a58c5af19ff0d6f44f6e9fe31e33a2c92223f77e
  6. Affected versionversion=f5778c398713692a16150ae96e5c8270bab8399f <ac2f14e4705d020f04e806efa0d49ab8dc2b145f

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=5.1; version=f5778c398713692a16150ae96e5c8270bab8399f <078fae8f50adebb903ccf2252b44391324571e78; version=f5778c398713692a16150ae96e5c8270bab8399f <85fd46ee26a11841c670449508025965f61ce131; version=f5778c398713692a16150ae96e5c8270bab8399f <a34d456934fe42e4da5d2cc07787bf418bee99c6; version=f5778c398713692a16150ae96e5c8270bab8399f <a58c5af19ff0d6f44f6e9fe31e33a2c92223f77e; version=f5778c398713692a16150ae96e5c8270bab8399f <ac2f14e4705d020f04e806efa0d49ab8dc2b145f

Published CVSS scores

8.1kernel.orgCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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