CyberSecBulletin
CVE-2026-23456NVD status: Modified

Linux: Out-of-bounds Read

Published Updated By the CyberSecBulletin desk

CVE-2026-23456 is a high-severity out-of-bounds read vulnerability in Linux, with a CVSS 3.1 base score of 8.2 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions a2cd54b9348e485d338b3c132338a4410c99afaf, c95dc674ebf01ecfb40388b6facfc89b81fed3b7, 41b417ff73a24b2c68134992cc44c88db27f482d 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 0.54% 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 a2cd54b9348e485d338b3c132338a4410c99afaf or c95dc674ebf01ecfb40388b6facfc89b81fed3b7 or 41b417ff73a24b2c68134992cc44c88db27f482d or 52235bf88159a1ef16434ab49e47e99c8a09ab20, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.253 or 5.15.203 or 6.1.167 or 6.6.130, 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.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux5e35941d990123f155b02d5663e51a24f816b6f3 up to, but not including, a2cd54b9348e485d338b3c132338a4410c99afaf; 5e35941d990123f155b02d5663e51a24f816b6f3 up to, but not including, c95dc674ebf01ecfb40388b6facfc89b81fed3b7; 5e35941d990123f155b02d5663e51a24f816b6f3 up to, but not including, 41b417ff73a24b2c68134992cc44c88db27f482d; 5e35941d990123f155b02d5663e51a24f816b6f3 up to, but not including, 52235bf88159a1ef16434ab49e47e99c8a09ab20; 5e35941d990123f155b02d5663e51a24f816b6f3 up to, but not including, 774a434f8c9c8602a976b2536f65d0172a07f4d2; 5e35941d990123f155b02d5663e51a24f816b6f3 up to, but not including, 6bce72daeccca9aa1746e92d6c3d4784e71f2ebb; 5e35941d990123f155b02d5663e51a24f816b6f3 up to, but not including, fb6c3596823ec5dd09c2123340330d7448f51a59; 5e35941d990123f155b02d5663e51a24f816b6f3 up to, but not including, 1e3a3593162c96e8a8de48b1e14f60c3b57fca8a; and 1 more rangesa2cd54b9348e485d338b3c132338a4410c99afaf, c95dc674ebf01ecfb40388b6facfc89b81fed3b7, 41b417ff73a24b2c68134992cc44c88db27f482d, 52235bf88159a1ef16434ab49e47e99c8a09ab20, 774a434f8c9c8602a976b2536f65d0172a07f4d2, 6bce72daeccca9aa1746e92d6c3d4784e71f2ebb
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)V3.1.6 and later; V3.1.5 and later; V3.1.7 and laterNot stated
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0)V3.1.6 and later; V3.1.5 and later; V3.1.7 and laterNot stated
SiemensSIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0)V3.1.6 and later; V3.1.5 and later; V3.1.7 and laterNot stated
SiemensSIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0)V3.1.6 and later; V3.1.5 and later; V3.1.7 and laterNot stated
SiemensSIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0)V3.1.6 and later; V3.1.5 and later; V3.1.7 and laterNot stated
LinuxLinux Kernel2.6.17 up to, but not including, 5.10.253; 5.11 up to, but not including, 5.15.203; 5.16 up to, but not including, 6.1.167; 6.2 up to, but not including, 6.6.130; 6.7 up to, but not including, 6.12.78; 6.13 up to, but not including, 6.18.20; 6.19 up to, but not including, 6.19.10; 7.05.10.253, 5.15.203, 6.1.167, 6.6.130, 6.12.78, 6.18.20

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
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
LowSome restricted data 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:N/S:U/C:L/I:N/A:H. Scored by CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack_h323: fix OOB read in decode_int() CONS case In decode_int(), the CONS case calls get_bits(bs, 2) to read a length value, then calls get_uint(bs, len) without checking that len bytes remain in the buffer. The existing boundary check only validates the 2 bits for get_bits(), not the subsequent 1-4 bytes that get_uint() reads. This allows a malformed H.323/RAS packet to cause a 1-4 byte slab-out-of-bounds read. Add a boundary check for len bytes after get_bits() and before get_uint().

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: yes, 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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