CVE-2021-47107Network attack vector

Kernel memory corruption via undersized READDIR count

Published Mar 4, 2024 · Updated Aug 5, 2026

Out-of-bounds write in Linux NFSD 5.13 allows remote attackers to corrupt kernel memory via a crafted NFSv2 or NFSv3 READDIR request. The init_dirlist helpers subtract protocol overhead from an unchecked count, underflow the reply length, and let xdr_reserve_space write past the allocated buffer. The NFS server must be enabled and reachable; a client allowed to issue READDIR can trigger a kernel crash or corrupt adjacent kernel memory.

CVSS severity9.8
Critical
EPSS probability0.85%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Out-of-bounds write in Linux NFSD 5.13 allows remote attackers to corrupt kernel memory via a crafted NFSv2 or NFSv3 READDIR request. The init_dirlist helpers subtract protocol overhead from an unchecked count, underflow the reply length, and let xdr_reserve_space write past the allocated buffer. The NFS server must be enabled and reachable; a client allowed to issue READDIR can trigger a kernel crash or corrupt adjacent kernel memory.

The record

CVE
CVE-2021-47107
Published
Mar 4, 2024
Updated
Aug 5, 2026
Vendor
Siemens
Product
SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
Classifications
CWE-120, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 4, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

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=37aa5e64022243e721b8334122997881177a4cfc <9e291a6a28d32545ed2fd959a8165144d1724df1; version=5.13; version=7f87fc2d34d475225e78b7f5c4eabb121f4282b2 <53b1119a6e5028b125f431a0116ba73510d82a72; version=7f87fc2d34d475225e78b7f5c4eabb121f4282b2 <eabc0aab98e5218ceecd82069b0d6fdfff5ee885

Published CVSS scores

9.8Linux kernel CNACVSS:3.1/AV:N/AC:L/PR:N/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
T1190Exploit Public-Facing Application

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo