CVE-2025-39703

System crash via undersized HSR frame

Published Sep 5, 2025 · Updated Aug 5, 2026

Improper input validation in the HSR receive path allows adjacent attackers to crash affected Linux kernels and SIMATIC CN 4100 before 5.0. hsr_handle_frame sets the network-header offset for an incomplete HSR tag without verifying that the skb contains both Ethernet and HSR headers, causing later transformations to leave insufficient headroom for skb_push. Exploitation requires an HSR-configured interface reachable at Layer 2 and results in a kernel panic that interrupts the device or host.

CVSS severity6.5
Medium
EPSS probability0.36%
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 HSR receive path allows adjacent attackers to crash affected Linux kernels and SIMATIC CN 4100 before 5.0. hsr_handle_frame sets the network-header offset for an incomplete HSR tag without verifying that the skb contains both Ethernet and HSR headers, causing later transformations to leave insufficient headroom for skb_push. Exploitation requires an HSR-configured interface reachable at Layer 2 and results in a kernel panic that interrupts the device or host.

The record

CVE
CVE-2025-39703
Published
Sep 5, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-1286, T1499.004
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 5, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 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=48b491a5cc74333c4a6a82fe21cea42c055a3b0b <3ae272ab523dd6bdc26e879027ed79feac9dd1b3
  2. Affected versionversion=48b491a5cc74333c4a6a82fe21cea42c055a3b0b <61009439e4bd8d74e705ee15940760321be91d8a
  3. Affected versionversion=48b491a5cc74333c4a6a82fe21cea42c055a3b0b <7af76e9d18a9fd6f8611b3313c86c190f9b6a5a7
  4. Affected versionversion=48b491a5cc74333c4a6a82fe21cea42c055a3b0b <acd69b597bd3f76d3b3d322b84082226c00eeaa4
  5. Affected versionversion=48b491a5cc74333c4a6a82fe21cea42c055a3b0b <b117c41b00902c1a7e24347c405cb82504aeae0b
  6. Affected versionversion=48b491a5cc74333c4a6a82fe21cea42c055a3b0b <b640188b8a6690e685939053c7efdbc7818b5f4e
  7. Affected versionversion=4ffd1d4a6b306ff69cbe412d2c54d2dd349ff436
  8. Affected versionversion=5.10.42 <5.10.241
  9. Affected versionversion=5.12.9 <5.13
  10. Affected versionversion=5.13
  11. Affected versionversion=f6442ee08fe66c8e45c4f246531a2aaf4f17a7a7 <8d9bc4a375a1ba05f7dfa0407de8e510ab9bd14d

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=48b491a5cc74333c4a6a82fe21cea42c055a3b0b <3ae272ab523dd6bdc26e879027ed79feac9dd1b3; version=48b491a5cc74333c4a6a82fe21cea42c055a3b0b <61009439e4bd8d74e705ee15940760321be91d8a; version=48b491a5cc74333c4a6a82fe21cea42c055a3b0b <7af76e9d18a9fd6f8611b3313c86c190f9b6a5a7; version=48b491a5cc74333c4a6a82fe21cea42c055a3b0b <acd69b597bd3f76d3b3d322b84082226c00eeaa4; version=48b491a5cc74333c4a6a82fe21cea42c055a3b0b <b117c41b00902c1a7e24347c405cb82504aeae0b; version=48b491a5cc74333c4a6a82fe21cea42c055a3b0b <b640188b8a6690e685939053c7efdbc7818b5f4e; version=4ffd1d4a6b306ff69cbe412d2c54d2dd349ff436; version=5.10.42 <5.10.241; version=5.12.9 <5.13; version=5.13; version=f6442ee08fe66c8e45c4f246531a2aaf4f17a7a7 <8d9bc4a375a1ba05f7dfa0407de8e510ab9bd14d
Siemens · SIMATIC CN 4100version=0 <V5.0

Published CVSS scores

6.5Siemens ProductCERTCVSS:3.1/AV:A/AC:L/PR:N/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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1286Improper Validation of Syntactic Correctness of Input
T1499.004Endpoint Denial of Service: Application or System Exploitation

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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