CyberSecBulletin
CVE-2026-68100NVD status: Received

Linux: Out-of-bounds Read

Published Updated By the CyberSecBulletin desk

CVE-2026-68100 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 attacker with a low-privileged account, without any action from a user. The record lists versions 26cb845e22a00c85bf566337417fa33492395f10, e31fada5143784bc05c7ae44c79eed9b7a2e147e, fb3dc8e6da46a1ccad1956cda57de29d9b3033e0 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 0.43% 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 26cb845e22a00c85bf566337417fa33492395f10 or e31fada5143784bc05c7ae44c79eed9b7a2e147e or fb3dc8e6da46a1ccad1956cda57de29d9b3033e0 or b6d3cc6a524416dfdb2b47e4bba2e7e20011d056, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxe2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 up to, but not including, 26cb845e22a00c85bf566337417fa33492395f10; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 up to, but not including, e31fada5143784bc05c7ae44c79eed9b7a2e147e; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 up to, but not including, fb3dc8e6da46a1ccad1956cda57de29d9b3033e0; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 up to, but not including, b6d3cc6a524416dfdb2b47e4bba2e7e20011d056; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 up to, but not including, 5acbd3012fd4a7ccfebd91ea6f784120084eb897; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 up to, but not including, 47f0b34f6bc98ed85bfdc293e8f3e432ec24958d; 5.1526cb845e22a00c85bf566337417fa33492395f10, e31fada5143784bc05c7ae44c79eed9b7a2e147e, fb3dc8e6da46a1ccad1956cda57de29d9b3033e0, b6d3cc6a524416dfdb2b47e4bba2e7e20011d056, 5acbd3012fd4a7ccfebd91ea6f784120084eb897, 47f0b34f6bc98ed85bfdc293e8f3e432ec24958d

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
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
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:L/UI:N/S:U/C:H/I:N/A:H. Scored by CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: validate num_subauth when copying ACE in set_ntacl_dacl set_ntacl_dacl() copies each ACE from the attacker-controlled stored security descriptor verbatim into the response DACL without checking sid.num_subauth. The ACE bytes (including an unchecked num_subauth) originate from an authenticated SMB2_SET_INFO(SecInfo=DACL) that is stored raw via ksmbd_vfs_set_sd_xattr(); parse_dacl() rejects a bad ACE with `break` rather than an error, so parse_sec_desc() still returns success and the malformed SD reaches the xattr intact. On a subsequent SMB2_QUERY_INFO(SecInfo=DACL) for an inode carrying a POSIX access ACL, build_sec_desc() -> set_ntacl_dacl() -> set_posix_acl_entries_dacl() walks the copied ACEs and reads ntace->sid.sub_auth[ntace->sid.num_subauth - 1] with num_subauth taken straight from the stored SD. Since sub_auth[] is fixed at SID_MAX_SUB_AUTHORITIES (15), a crafted num_subauth (e.g. 255) drives an out-of-bounds heap read of ~1 KB with an offset fully controlled by an authenticated client. The sibling functions already gate this field: parse_dacl() -- num_subauth == 0 || > SID_MAX_SUB_AUTHORITIES parse_sid() -- num_subauth > SID_MAX_SUB_AUTHORITIES smb_copy_sid() -- min_t(u8, num_subauth, SID_MAX_SUB_AUTHORITIES) set_ntacl_dacl() is the lone inconsistent path that omits the check. Add the same num_subauth validation in set_ntacl_dacl() before copying the ACE, matching the gate already enforced by parse_dacl().

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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