HighCVE-2026-31709

Linux Kernel: security vulnerability (CVE-2026-31709)

Published 01.05.2026Last modified 19.10.2026Sources: Debian LTS, Ubuntu, Debian, Siemens ProductCERT, CVE.org, Msrc Update Guide, EUVD, BSI

What is affected, what to do

Update Linux Kernel to version 5.15.210, Linux Kernel to version 6.1.176, Linux Kernel to version 6.6.140.

Affected: Linux Kernel lt 5.12..5.15.210
Linux Kernel lt 5.16..6.1.176
Linux Kernel lt 6.2..6.6.140
Linux Kernel lt 6.7..6.12.86
Linux Kernel lt 6.13..6.18.35
Linux Kernel lt 6.19..7.0.2
Fixed in: Linux Kernel 5.15.210
Linux Kernel 6.1.176
Linux Kernel 6.6.140
Linux Kernel 6.12.86
Linux Kernel 6.18.35
Linux Kernel 7.0.2
Linux Kernel 7.1

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Metrics

8.8

Priority

XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

Source: NVD, CVSS v3

8.8

CVSS v3

Severity High on the scale from 0 to 10.

Source: Debian LTS, Ubuntu, Debian, Siemens ProductCERT, CVE.org, Msrc Update Guide, EUVD, BSI

0.3 %

EPSS score

Low — model estimates < 1% exploitation likelihood.

Source: FIRST EPSS, percentile 28.0

Show all metrics

Severity: High
Priority (0–325) The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first? Read in glossary: 67.12 Methodology
Exploit maturity An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack. Read in glossary: no public PoC known
XIEM Effective CVSS XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command. Read in glossary: 8.8 Methodology
CVSS v3 CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions. Read in glossary: 8.8
EPSS score The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“. Read in glossary: 0.3 %; Low — model estimates < 1% exploitation likelihood.
EPSS percentile The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking. Read in glossary: 28.0; Elevated — this CVE ranks above at least 10% of all CVEs scored today.
KEV status The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching. Read in glossary: —
Published: 01.05.2026
CISA assessment (SSVC): Exploitation: none known · not automatable · Technical impact: total; Source: CISA Vulnrichment, as of 16 October 2026
CWE CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect. Read in glossary: CWE-125

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2 NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management. Read in glossary: High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
CRA The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates. Read in glossary: From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001 ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security. Read in glossary: Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: validate the whole DACL before rewriting it in cifsacl build_sec_desc() and id_mode_to_cifs_acl() derive a DACL pointer from a server-supplied dacloffset and then use the incoming ACL to rebuild the chmod/chown security descriptor. The original fix only checked that the struct smb_acl header fits before reading dacl_ptr->size or dacl_ptr->num_aces. That avoids the immediate header-field OOB read, but the rewrite helpers still walk ACEs based on pdacl->num_aces with no structural validation of the incoming DACL body. A malicious server can return a truncated DACL that still contains a header, claims one or more ACEs, and then drive replace_sids_and_copy_aces() or set_chmod_dacl() past the validated extent while they compare or copy attacker-controlled ACEs. Factor the DACL structural checks into validate_dacl(), extend them to validate each ACE against the DACL bounds, and use the shared validator before the chmod/chown rebuild paths. parse_dacl() reuses the same validator so the read-side parser and write-side rewrite paths agree on what constitutes a well-formed incoming DACL.

Source: Debian LTS Advisories, Ubuntu Security Notices, Debian Security Advisories, siemens_advisory, NVD (NIST), CVE.org (MITRE), cvelistv5, Microsoft Security Update Guide, ENISA EUVD, BSI WID Portal, BSI CSAF

Affected products

The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

Affected products
		Affected versions	Fixed in
Linux	Linux	`6.2 – < 6.6.140` `6.13 – < 6.18.35` `5.12 – < 5.15.210` `—` `6.19 – < 7.0.2` `5.16 – < 6.1.176` `6.7 – < 6.12.86`	`6.6.140` `6.18.35` `5.15.210` `7.1` `7.0.2` `6.1.176` `6.12.86`
Microsoft	Azure Linux	`azl3`	—
Siemens	SIMATIC S7	`1500 TM MFP V1.1.1 GNU/Linux subsystem`	—

Vendors and products

Affected operating systems

Affected operating systems

Linux	debian	linux	`bookworm`
Linux	debian	linux	`trixie`
Linux	debian	linux-6.1	`bullseye`
Linux	linux	linux_kernel	—

Weakness classes (CWE)

CWE-125Out-of-bounds Read
Base
The product reads data past the end, or before the beginning, of the intended buffer.
Entry at MITRE CWE-125

References & sources

git.kernel.orgstable/c/8e47d297e7cf9a6029a0d38e7b22faba7d7aaf12euvd
git.kernel.orgstable/c/d92f3f0b22414e7515696a02224d0af55e3004a3euvd
git.kernel.orgstable/c/b78db9bddc84136f6a0bb49e8883cf200dfb87a8euvd, Patch
git.kernel.orgstable/c/0a8cf165566ba55a39fd0f4de172119dd646d39aeuvd, Patch
git.kernel.orgstable/c/b8603d9ae6c9087662b098619996bc4a8064319d
git.kernel.orgstable/c/c2abdebf72000a64603ced84d36ccbd164f11391
git.kernel.orgstable/c/ff0ca46b13b9ef6edbcd238a3b6caacfef8ba0e5
access.redhat.comsecurity/cve/CVE-2026-31709Vulnerability database, x_refsource_REDHAT
bugzilla.redhat.comRHBZ#2464476Issue tracking, x_refsource_REDHAT
security.access.redhat.comdata/csaf/v2/vex/2026/cve-2026-31709.jsonx_sadp-csaf-vex
access.redhat.comerrata/RHSA-2026:24343Vendor advisory, x_refsource_REDHAT
access.redhat.comerrata/RHSA-2026:23329Vendor advisory, x_refsource_REDHAT
access.redhat.comerrata/RHSA-2026:22940Vendor advisory, x_refsource_REDHAT
access.redhat.comerrata/RHSA-2026:23237Vendor advisory, x_refsource_REDHAT
access.redhat.comerrata/RHSA-2026:23224Vendor advisory, x_refsource_REDHAT
access.redhat.comerrata/RHSA-2026:21556Vendor advisory, x_refsource_REDHAT
access.redhat.comerrata/RHSA-2026:21706Vendor advisory, x_refsource_REDHAT
access.redhat.comerrata/RHSA-2026:21745Vendor advisory, x_refsource_REDHAT
access.redhat.comerrata/RHSA-2026:22900Vendor advisory, x_refsource_REDHAT
Siemens ProductCERTproductcert/html/ssa-784472.html

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

19.10.2026Record modifiedCISA ADP
Weakness type: CWE-125
Show the original change
Individual changes of this event as published by NVD
Type Action Before After
Weakness type (CWE) added
—
CWE-125
Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

Individual changes of this event as published by NVD
Type	Action	Before	After
Weakness type (CWE)	added	—	CWE-125

16.10.2026Record modifiedCISA ADP

CISA assessment (SSVC): exploitation: none known, automatable: no

Show the original change

Individual changes of this event as published by NVD
Type	Action	Before	After
SSVC assessment	added	—	{"id":"CVE-2026-31709","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:12:47.844968Z"}

Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

15.10.2026Record modifiedLinux

New references:

and 3 more references

Show 16 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Reference	added	—	https://git.kernel.org/stable/c/0a8cf165566ba55a39fd0f4de172119dd646d39a
Reference	added	—	https://git.kernel.org/stable/c/8e47d297e7cf9a6029a0d38e7b22faba7d7aaf12
Reference	added	—	https://git.kernel.org/stable/c/b78db9bddc84136f6a0bb49e8883cf200dfb87a8
Reference	added	—	https://git.kernel.org/stable/c/b8603d9ae6c9087662b098619996bc4a8064319d
Reference	added	—	https://git.kernel.org/stable/c/c2abdebf72000a64603ced84d36ccbd164f11391
Reference	added	—	https://git.kernel.org/stable/c/d92f3f0b22414e7515696a02224d0af55e3004a3
Reference	added	—	https://git.kernel.org/stable/c/ff0ca46b13b9ef6edbcd238a3b6caacfef8ba0e5
Reference	removed	https://git.kernel.org/stable/c/0a8cf165566ba55a39fd0f4de172119dd646d39a	—
Reference	removed	https://git.kernel.org/stable/c/8e47d297e7cf9a6029a0d38e7b22faba7d7aaf12	—
Reference	removed	https://git.kernel.org/stable/c/b78db9bddc84136f6a0bb49e8883cf200dfb87a8	—
Reference	removed	https://git.kernel.org/stable/c/b8603d9ae6c9087662b098619996bc4a8064319d	—
Reference	removed	https://git.kernel.org/stable/c/c2abdebf72000a64603ced84d36ccbd164f11391	—
Reference	removed	https://git.kernel.org/stable/c/d92f3f0b22414e7515696a02224d0af55e3004a3	—
Reference	removed	https://git.kernel.org/stable/c/ff0ca46b13b9ef6edbcd238a3b6caacfef8ba0e5	—
Reference type	removed	https://git.kernel.org/stable/c/0a8cf165566ba55a39fd0f4de172119dd646d39a Types: Patch	—
Reference type	removed	https://git.kernel.org/stable/c/b78db9bddc84136f6a0bb49e8883cf200dfb87a8 Types: Patch	—

Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

15.10.2026Record modifiedRed Hat ADP

New references:

and 8 more references

Show 24 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Reference	added	—	https://access.redhat.com/errata/RHSA-2026:21556
Reference	added	—	https://access.redhat.com/errata/RHSA-2026:21706
Reference	added	—	https://access.redhat.com/errata/RHSA-2026:21745
Reference	added	—	https://access.redhat.com/errata/RHSA-2026:22900
Reference	added	—	https://access.redhat.com/errata/RHSA-2026:22940
Reference	added	—	https://access.redhat.com/errata/RHSA-2026:23224
Reference	added	—	https://access.redhat.com/errata/RHSA-2026:23237
Reference	added	—	https://access.redhat.com/errata/RHSA-2026:23329
Reference	added	—	https://access.redhat.com/errata/RHSA-2026:24343
Reference	added	—	https://access.redhat.com/security/cve/CVE-2026-31709
Reference	added	—	https://bugzilla.redhat.com/show_bug.cgi?id=2464476
Reference	added	—	https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31709.json
Reference	removed	https://access.redhat.com/errata/RHSA-2026:21556	—
Reference	removed	https://access.redhat.com/errata/RHSA-2026:21706	—
Reference	removed	https://access.redhat.com/errata/RHSA-2026:21745	—
Reference	removed	https://access.redhat.com/errata/RHSA-2026:22900	—
Reference	removed	https://access.redhat.com/errata/RHSA-2026:22940	—
Reference	removed	https://access.redhat.com/errata/RHSA-2026:23224	—
Reference	removed	https://access.redhat.com/errata/RHSA-2026:23237	—
Reference	removed	https://access.redhat.com/errata/RHSA-2026:23329	—
Reference	removed	https://access.redhat.com/errata/RHSA-2026:24343	—
Reference	removed	https://access.redhat.com/security/cve/CVE-2026-31709	—
Reference	removed	https://bugzilla.redhat.com/show_bug.cgi?id=2464476	—
Reference	removed	https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31709.json	—

Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

15.10.2026Record modifiedSiemens ADP

New references:

https://cert-portal.siemens.com/productcert/html/ssa-784472.html

Show 2 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Affected versions (publisher)	added	—	New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/31xxx/CVE-2026-31709.json">CVE-2026-31709</a>
Reference	added	—	https://cert-portal.siemens.com/productcert/html/ssa-784472.html

Source identifier: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e

Show one older change

19.06.2026Record modifiedLinux

New references:

Show 3 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Reference	added	—	https://git.kernel.org/stable/c/b8603d9ae6c9087662b098619996bc4a8064319d
Reference	added	—	https://git.kernel.org/stable/c/c2abdebf72000a64603ced84d36ccbd164f11391
Affected versions (publisher)	changed	Linux, Linux	Linux, Linux

Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

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<a href="https://intel.neosec.eu/en/cve/CVE-2026-31709"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-31709.svg?lang=en" alt="CVE-2026-31709 – NEOSEC Intel" height="20"></a>