CVE-2025-21863

Unspecified local impact via speculative opcode indexing

Published Mar 12, 2025 · Updated Sep 8, 2026

Improper input validation in Linux kernel io_uring allows local users to cause unspecified impact through a crafted SQE opcode. The io_init_req path bounds-checks the user-controlled sqe->opcode but uses it to select operation tables without array_index_nospec sanitization, permitting speculative out-of-bounds indexing. Local low-privileged access to io_uring is required; public advisories do not describe the exact post-trigger consequence.

CVSS severity7.8
High
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Linux kernel io_uring allows local users to cause unspecified impact through a crafted SQE opcode. The io_init_req path bounds-checks the user-controlled sqe->opcode but uses it to select operation tables without array_index_nospec sanitization, permitting speculative out-of-bounds indexing. Local low-privileged access to io_uring is required; public advisories do not describe the exact post-trigger consequence.

The record

CVE
CVE-2025-21863
Published
Mar 12, 2025
Updated
Sep 8, 2026
Vendor
Siemens
Product
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP
Classifications
CWE-20
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 12, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 8, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=V3.1.6 <*

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Siemens · SIPLUS S7-1500 CPU 1518-4 PN/DP MFPversion=V3.1.6 <*
The Linux Kernel Organization · Linuxversion=5.6; version=d3656344fea0339fb0365c8df4d2beba4e0089cd <18eae8420081ef8e043ad455937bfb470ef08607; version=d3656344fea0339fb0365c8df4d2beba4e0089cd <1e988c3fe1264708f4f92109203ac5b1d65de50b; version=d3656344fea0339fb0365c8df4d2beba4e0089cd <506b9b5e8c2d2a411ea8fe361333f5081c56d23a; version=d3656344fea0339fb0365c8df4d2beba4e0089cd <87e9eef43c758da267f6332678058a79764c7eba; version=d3656344fea0339fb0365c8df4d2beba4e0089cd <b9826e3b26ec031e9063f64a7c735449c43955e4; version=d3656344fea0339fb0365c8df4d2beba4e0089cd <d261ead565a080e3411b0dd04e6d58a52471cac8; version=d3656344fea0339fb0365c8df4d2beba4e0089cd <fdbfd52bd8b85ed6783365ff54c82ab7067bd61b
Siemens · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPversion=V3.1.6 <*
Siemens · SIMATIC S7-1500 CPU 1518-4 PN/DP MFPversion=V3.1.6 <*

Published CVSS scores

7.8Siemens ProductCERTCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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