CyberSecBulletin
CVE-2026-31447NVD status: Modified

In the Linux kernel, the following vulnerability has been resolved: ext4: reject mount if…

Published Updated By the CyberSecBulletin desk

CVE-2026-31447 is a high-severity improper input validation 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 unauthenticated attacker, but only if a user takes part, for example by opening a link or file. The record lists versions 5ad6d994255e27a3254079dfb50ca861fc31f2d0, 3a926957cc95899ef88529710836edadc03c71a1, 7b58c110b4e1f028eb38eec9ed3555e9be81c8b0 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 0.14% 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 5ad6d994255e27a3254079dfb50ca861fc31f2d0 or 3a926957cc95899ef88529710836edadc03c71a1 or 7b58c110b4e1f028eb38eec9ed3555e9be81c8b0 or b77de3fceafbb39f30e4ff5dc986f863d5456417, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.253 or 5.15.203 or 6.1.168 or 6.6.131, whichever matches your release line, or a later version.
  3. 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
LinuxLinux281b59959707dfae03ce038cdf231bf4904e170c up to, but not including, 5ad6d994255e27a3254079dfb50ca861fc31f2d0; 281b59959707dfae03ce038cdf231bf4904e170c up to, but not including, 3a926957cc95899ef88529710836edadc03c71a1; 281b59959707dfae03ce038cdf231bf4904e170c up to, but not including, 7b58c110b4e1f028eb38eec9ed3555e9be81c8b0; 281b59959707dfae03ce038cdf231bf4904e170c up to, but not including, b77de3fceafbb39f30e4ff5dc986f863d5456417; 281b59959707dfae03ce038cdf231bf4904e170c up to, but not including, d787d3ae96648dc14a3b7ca8fde817177e82c1c7; 281b59959707dfae03ce038cdf231bf4904e170c up to, but not including, ad1f6d608f33f59d21a3d025615d6786a6443998; 281b59959707dfae03ce038cdf231bf4904e170c up to, but not including, 7d5b04290156c3fc316eecc86a4f9d201ab7d44a; 281b59959707dfae03ce038cdf231bf4904e170c up to, but not including, 3822743dc20386d9897e999dbb990befa3a5b3f8; and 1 more ranges5ad6d994255e27a3254079dfb50ca861fc31f2d0, 3a926957cc95899ef88529710836edadc03c71a1, 7b58c110b4e1f028eb38eec9ed3555e9be81c8b0, b77de3fceafbb39f30e4ff5dc986f863d5456417, d787d3ae96648dc14a3b7ca8fde817177e82c1c7, ad1f6d608f33f59d21a3d025615d6786a6443998
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 Kernel3.2 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, 6.1.168; 6.2 up to, but not including, 6.6.131; 6.7 up to, but not including, 6.12.80; 6.13 up to, but not including, 6.18.21; 6.19 up to, but not including, 6.19.11; 7.05.10.253, 5.15.203, 6.1.168, 6.6.131, 6.12.80, 6.18.21

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
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
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:N/UI:R/S:U/C:H/I:H/A:H. Scored by CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: ext4: reject mount if bigalloc with s_first_data_block != 0 bigalloc with s_first_data_block != 0 is not supported, reject mounting it.

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

The underlying weakness: Improper Input Validation

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

How developers prevent this class of flaw

  • Consider using language-theoretic security (LangSec) techniques that characterize inputs using a formal language and build recognizers for that language. This effectively requires parsing to be a distinct layer that effectively enforces a boundary between raw input and internal data representations, instead of allowing parser code to be scattered throughout the program, where it could be subject to errors or inconsistencies that create weaknesses.
  • Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
  • Understand all the potential areas where untrusted inputs can enter the product, including but not limited to: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.

More Improper Input Validation vulnerabilities (CWE-20)

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 Improper Input Validation vulnerabilities

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