CyberSecBulletin
CVE-2026-23243NVD status: Modified

Linux: Out-of-bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2026-23243 is a high-severity out-of-bounds write vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 1371ef6b1ecf3676b8942f5dfb3634fb0648128e, 362e45fd9069ffa1523f9f1633b606ebf72060d7, 6eb2919474ca105c5b13d19574e25f0ddcf19ca2 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 0.19% 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 1371ef6b1ecf3676b8942f5dfb3634fb0648128e or 362e45fd9069ffa1523f9f1633b606ebf72060d7 or 6eb2919474ca105c5b13d19574e25f0ddcf19ca2 or a6a3e4af10993cb9e4b8f0548680aba0ab5f3b0d, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.252 or 5.15.202 or 6.1.165 or 6.6.128, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux2be8e3ee8efd6f99ce454115c29d09750915021a up to, but not including, 1371ef6b1ecf3676b8942f5dfb3634fb0648128e; 2be8e3ee8efd6f99ce454115c29d09750915021a up to, but not including, 362e45fd9069ffa1523f9f1633b606ebf72060d7; 2be8e3ee8efd6f99ce454115c29d09750915021a up to, but not including, 6eb2919474ca105c5b13d19574e25f0ddcf19ca2; 2be8e3ee8efd6f99ce454115c29d09750915021a up to, but not including, a6a3e4af10993cb9e4b8f0548680aba0ab5f3b0d; 2be8e3ee8efd6f99ce454115c29d09750915021a up to, but not including, 9c80d688f402539dfc8f336de1380d6b4ee14316; 2be8e3ee8efd6f99ce454115c29d09750915021a up to, but not including, 205955f29c26330b1dc7fdeadd5bb97c38e26f56; 2be8e3ee8efd6f99ce454115c29d09750915021a up to, but not including, 52ab82cc5cf8ada5c3fb6ffe8f32fdb2fc27a34b; 2be8e3ee8efd6f99ce454115c29d09750915021a up to, but not including, 5551b02fdbfd85a325bb857f3a8f9c9f33397ed2; and 1 more ranges1371ef6b1ecf3676b8942f5dfb3634fb0648128e, 362e45fd9069ffa1523f9f1633b606ebf72060d7, 6eb2919474ca105c5b13d19574e25f0ddcf19ca2, a6a3e4af10993cb9e4b8f0548680aba0ab5f3b0d, 9c80d688f402539dfc8f336de1380d6b4ee14316, 205955f29c26330b1dc7fdeadd5bb97c38e26f56
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 Kernel2.6.24.1 up to, but not including, 5.10.252; 5.11 up to, but not including, 5.15.202; 5.16 up to, but not including, 6.1.165; 6.2 up to, but not including, 6.6.128; 6.7 up to, but not including, 6.12.75; 6.13 up to, but not including, 6.18.14; 6.19 up to, but not including, 6.19.4; 2.6.245.10.252, 5.15.202, 6.1.165, 6.6.128, 6.12.75, 6.18.14

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
LocalThe attacker needs local access or must trick a user into running something.
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
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

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

Official description

In the Linux kernel, the following vulnerability has been resolved: RDMA/umad: Reject negative data_len in ib_umad_write ib_umad_write computes data_len from user-controlled count and the MAD header sizes. With a mismatched user MAD header size and RMPP header length, data_len can become negative and reach ib_create_send_mad(). This can make the padding calculation exceed the segment size and trigger an out-of-bounds memset in alloc_send_rmpp_list(). Add an explicit check to reject negative data_len before creating the send buffer. KASAN splat: [ 211.363464] BUG: KASAN: slab-out-of-bounds in ib_create_send_mad+0xa01/0x11b0 [ 211.364077] Write of size 220 at addr ffff88800c3fa1f8 by task spray_thread/102 [ 211.365867] ib_create_send_mad+0xa01/0x11b0 [ 211.365887] ib_umad_write+0x853/0x1c80

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

The underlying weakness: Out-of-bounds Write

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

How developers prevent this class of flaw

  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
  • Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.

More Out-of-bounds Write vulnerabilities (CWE-787)

Timeline

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

References

Recent Out-of-bounds Write vulnerabilities

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