CVE-2021-43083Network attack vector

Buffer overflow via underflowed TCP response length

Published Dec 19, 2021 · Updated Aug 4, 2024

Buffer overflow in Apache PLC4X PLC4C 0.9.0 and earlier allows remote attackers to corrupt memory via a malicious device response. The PLC4C TCP transport lets invalid response content underflow an unsigned length value, causing subsequent response processing to exceed buffer bounds. Exploitation requires the PLC4C client to initiate a connection to a malicious device that returns the crafted content.

CVSS severity8.8
High
EPSS probability1.92%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer overflow in Apache PLC4X PLC4C 0.9.0 and earlier allows remote attackers to corrupt memory via a malicious device response. The PLC4C TCP transport lets invalid response content underflow an unsigned length value, causing subsequent response processing to exceed buffer bounds. Exploitation requires the PLC4C client to initiate a connection to a malicious device that returns the crafted content.

The record

CVE
CVE-2021-43083
Published
Dec 19, 2021
Updated
Aug 4, 2024
Vendor
Apache Software Foundation
Product
Apache PLC4X
Classifications
CWE-119, CWE-191, T1203
Attack vector
network
Privileges
Unavailable

Timeline

How it unfolded

  1. Dec 19, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record 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=PLC4C <=0.9.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesUnavailable in this record.

What is affected?

Apache Software Foundation · Apache PLC4Xversion=PLC4C <=0.9.0

Published CVSS scores

8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
6.5NIST NVDAV:N/AC:L/Au:S/C:P/I:P/A:P

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
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
CWE-191Integer Underflow (Wrap or Wraparound)
T1203Exploitation for Client Execution

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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