CVE-2021-47316Network attack vector

Remote crash via NULL dentry dereference

Published May 21, 2024 · Updated Aug 5, 2026

NULL pointer dereference in Linux 5.13 through 5.13.3 allows remote attackers to crash an NFS server via an NFSv3 ACL GETACL request. The nfs3svc_encode_getaclres reply encoder calls d_inode on a dentry before checking the response status, although error replies can leave that dentry NULL. Reachability requires the NFSv3 ACL service; the resulting kernel oops or panic interrupts the server host, including affected SIMATIC GNU/Linux subsystems.

CVSS severity7.5
High
EPSS probability0.62%
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 Linux 5.13 through 5.13.3 allows remote attackers to crash an NFS server via an NFSv3 ACL GETACL request. The nfs3svc_encode_getaclres reply encoder calls d_inode on a dentry before checking the response status, although error replies can leave that dentry NULL. Reachability requires the NFSv3 ACL service; the resulting kernel oops or panic interrupts the server host, including affected SIMATIC GNU/Linux subsystems.

The record

CVE
CVE-2021-47316
Published
May 21, 2024
Updated
Aug 5, 2026
Vendor
Siemens
Product
SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
Classifications
CWE-476, CWE-20, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 21, 2024CVE 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=20798dfe249a01ad1b12eec7dbc572db5003244a <650e6f383a6eb40f7c0a010982a74ab4b6893870; version=20798dfe249a01ad1b12eec7dbc572db5003244a <ab1016d39cc052064e32f25ad18ef8767a0ee3b8; version=5.13; version=d505e66191072748620fc0af038cea4e4da0e3cd <e79057d15d96ef19de4de6d7e479bae3d58a2a8d

Published CVSS scores

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

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
CWE-20Improper Input Validation
T1499Endpoint Denial of Service

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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