CVE-2025-21925

Host crash via shared LLC transmit buffer

Published Apr 1, 2025 · Updated Sep 8, 2026

Improper input validation in the Linux kernel LLC transmit path allows local users to crash hosts through crafted LLC socket traffic. llc_sap_action_send_test_c() calls skb_get() before dev_queue_xmit(), leaving a shared socket buffer that e1000's eth_skb_pad() attempts to expand. Exploitation requires local low-privileged access, LLC use, and a network device without IFF_TX_SKB_SHARING; the bounded result is a kernel crash.

CVSS severity5.5
Medium
EPSS probability0.22%
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 the Linux kernel LLC transmit path allows local users to crash hosts through crafted LLC socket traffic. llc_sap_action_send_test_c() calls skb_get() before dev_queue_xmit(), leaving a shared socket buffer that e1000's eth_skb_pad() attempts to expand. Exploitation requires local low-privileged access, LLC use, and a network device without IFF_TX_SKB_SHARING; the bounded result is a kernel crash.

The record

CVE
CVE-2025-21925
Published
Apr 1, 2025
Updated
Sep 8, 2026
Vendor
Siemens
Product
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP
Classifications
CWE-20, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 1, 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=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <056e8a46d79e22983bae4267e0d9c52927076f46; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <0f764208dc24ea043c3e20194d32aebf94f8459c; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <13f3f872627f0f27c31245524fc11367756240ad; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <17f86e25431ebc15aa9245ff156414fdad47822d; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <416e8b4c20c6398044e93008deefd563289f477d; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <64e6a754d33d31aa844b3ee66fb93ac84ca1565e; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <9b6f083db141ece0024be01526aa05aa978811cb; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <cd1c44327bbbd50fc24f2b38892f5f328b784d0f; version=2.6.12
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

5.5Siemens ProductCERTCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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