CyberSecBulletin
CVE-2026-31708NVD status: Modified

Linux: Out-of-bounds Read

Published Updated By the CyberSecBulletin desk

CVE-2026-31708 is a high-severity out-of-bounds read vulnerability in Linux, with a CVSS 3.1 base score of 8.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. The record lists versions e66bdc0704977ecee667a81d38255b579c2353d0, 9e203dbb5402897c43130fb171a2617008a91f45, 1dd757379997b71a328a4b591ffaf481acd0ead1 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.35% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to e66bdc0704977ecee667a81d38255b579c2353d0 or 9e203dbb5402897c43130fb171a2617008a91f45 or 1dd757379997b71a328a4b591ffaf481acd0ead1 or a34d456934fe42e4da5d2cc07787bf418bee99c6, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.6.136 or 6.12.84 or 6.18.25 or 7.0.2, whichever matches your release line, or a later version.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
  4. Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxf5778c398713692a16150ae96e5c8270bab8399f up to, but not including, e66bdc0704977ecee667a81d38255b579c2353d0; f5778c398713692a16150ae96e5c8270bab8399f up to, but not including, 9e203dbb5402897c43130fb171a2617008a91f45; f5778c398713692a16150ae96e5c8270bab8399f up to, but not including, 1dd757379997b71a328a4b591ffaf481acd0ead1; f5778c398713692a16150ae96e5c8270bab8399f up to, but not including, a34d456934fe42e4da5d2cc07787bf418bee99c6; f5778c398713692a16150ae96e5c8270bab8399f up to, but not including, ac2f14e4705d020f04e806efa0d49ab8dc2b145f; f5778c398713692a16150ae96e5c8270bab8399f up to, but not including, 078fae8f50adebb903ccf2252b44391324571e78; f5778c398713692a16150ae96e5c8270bab8399f up to, but not including, 85fd46ee26a11841c670449508025965f61ce131; f5778c398713692a16150ae96e5c8270bab8399f up to, but not including, a58c5af19ff0d6f44f6e9fe31e33a2c92223f77e; and 1 more rangese66bdc0704977ecee667a81d38255b579c2353d0, 9e203dbb5402897c43130fb171a2617008a91f45, 1dd757379997b71a328a4b591ffaf481acd0ead1, a34d456934fe42e4da5d2cc07787bf418bee99c6, ac2f14e4705d020f04e806efa0d49ab8dc2b145f, 078fae8f50adebb903ccf2252b44391324571e78
SiemensSIMATIC S7-1500 TM MFP - GNU/Linux subsystemall versionsNot stated
LinuxLinux Kernel5.1 up to, but not including, 6.6.136; 6.7 up to, but not including, 6.12.84; 6.13 up to, but not including, 6.18.25; 6.19 up to, but not including, 7.0.26.6.136, 6.12.84, 6.18.25, 7.0.2

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
RequiredA user must take an action such as opening a file or link.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
NoneNothing can be modified.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H. Scored by CNA.

Official 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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Out-of-bounds Read

The product reads data past the end, or before the beginning, of the intended buffer.

How developers prevent this class of flaw

  • Use a language that provides appropriate memory abstractions.

More Out-of-bounds Read vulnerabilities (CWE-125)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Out-of-bounds Read vulnerabilities

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