CVE-2025-21844Network attack vector

Kernel crash via unchecked SMB buffer allocation

Published Mar 12, 2025 · Updated Aug 5, 2026

NULL pointer dereference in the SMB client receive path in Linux allows remote attackers to crash the kernel via a crafted server response. receive_encrypted_standard() fails to check whether cifs_buf_get() or cifs_small_buf_get() returned NULL before copying response data into the buffer. An SMB share must already be mounted and accept an encrypted compounded response with a nonzero NextCommand; the bounded result is an oops, panic, or halt without reported data disclosure or modification.

CVSS severity7.5
High
EPSS probability0.61%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in the SMB client receive path in Linux allows remote attackers to crash the kernel via a crafted server response. receive_encrypted_standard() fails to check whether cifs_buf_get() or cifs_small_buf_get() returned NULL before copying response data into the buffer. An SMB share must already be mounted and accept an encrypted compounded response with a nonzero NextCommand; the bounded result is an oops, panic, or halt without reported data disclosure or modification.

The record

CVE
CVE-2025-21844
Published
Mar 12, 2025
Updated
Aug 5, 2026
Vendor
Siemens
Product
SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
Classifications
CWE-476, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 12, 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=0 <*

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Siemens · SIMATIC S7-1500 TM MFP - GNU/Linux subsystemversion=0 <*
The Linux Kernel Organization · Linuxversion=5.10.211 <5.10.235; version=5.15.150 <5.15.179; version=534733397da26de0303057ce0b93a22bda150365 <9e5d99a4cf2e23c716b44862975548415fae5391; version=6.1.69 <6.1.130; version=6.6.8 <6.6.80; version=6.7; version=858e73ff25639a0cc1f6f8d2587b62c045867e41 <f618aeb6cad2307e48a641379db610abcf593edf; version=9f528a8e68327117837b5e28b096f52af4c26a05 <24e8e4523d3071bc5143b0db9127d511489f7b3b; version=b03c8099a738a04d2343547ae6a04e5f0f63d3fa <f277e479eea3d1aa18bc712abe1d2bf3dece2e30; version=eec04ea119691e65227a97ce53c0da6b9b74b0b7 <554736b583f529ee159aa95af9a0cbc12b5ffc96; version=eec04ea119691e65227a97ce53c0da6b9b74b0b7 <860ca5e50f73c2a1cef7eefc9d39d04e275417f7; version=eec04ea119691e65227a97ce53c0da6b9b74b0b7 <a9b0b4b29877cb4dc5d0842b59b5ccbacddb85bd

Published CVSS scores

5.5Siemens ProductCERTCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
7.5Linux kernel CNACVSS:3.1/AV:N/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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499Endpoint Denial of Service

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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