CVE-2021-21869Public exploitNetwork attack vector

Code execution via unvalidated ProfileData deserialization

Published Aug 25, 2021 · Updated Aug 3, 2024

Unsafe deserialization in CODESYS GmbH's CODESYS Development System before 3.5.17.10 allows remote attackers to execute code via a crafted project file. The ProfileData setter in Engine.plugin passes profile.auxiliary bytes directly to BinaryFormatter.Deserialize without validating the serialized objects. Execution requires a local user to open the malicious project, and successful exploitation runs arbitrary commands in that user's context.

CVSS severity8.8
High
EPSS probability1.75%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Unsafe deserialization in CODESYS GmbH's CODESYS Development System before 3.5.17.10 allows remote attackers to execute code via a crafted project file. The ProfileData setter in Engine.plugin passes profile.auxiliary bytes directly to BinaryFormatter.Deserialize without validating the serialized objects. Execution requires a local user to open the malicious project, and successful exploitation runs arbitrary commands in that user's context.

The record

CVE
CVE-2021-21869
Published
Aug 25, 2021
Updated
Aug 3, 2024
Vendor
CODESYS GmbH
Product
CODESYS Development System
Classifications
CWE-502, T1204.002, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 25, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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=CODESYS GmbH CODESYS Development System 3.5.16, CODESYS GmbH CODESYS Development System 3.5.17

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

CODESYS GmbH · CODESYS Development Systemversion=CODESYS GmbH CODESYS Development System 3.5.16, CODESYS GmbH CODESYS Development System 3.5.17

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
8.8CODESYS GmbHCVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NIST NVDAV:N/AC:M/Au:N/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-502Deserialization of Untrusted Data
T1204.002User Execution: Malicious File
T1203Exploitation for Client Execution

Public exploit references

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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