How severe is CVE-2021-21867?

CVE-2021-21867 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-21867 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (74th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-21867?

CVE-2021-21867 primarily affects Codesys. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-21867?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-21867 published?

CVE-2021-21867 was published on 2021-08-18 and last updated on 2026-06-17.

CVE-2021-21867

CVE-2021-21867 is a high-severity vulnerability in Codesys with a CVSS 3.x base score of 7.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-502.

Key facts

Severity: High (CVSS 3.x base score 7.8)
CVSS v2: 6.8
EPSS exploit prediction: 2% (74th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-502
Affected product: Codesys
Published: 2021-08-18
Last modified: 2026-06-17

Description

An unsafe deserialization vulnerability exists in the ObjectManager.plugin ObjectStream.ProfileByteArray functionality of CODESYS GmbH CODESYS Development System 3.5.16 and 3.5.17. A specially crafted file can lead to arbitrary command execution. An attacker can provide a malicious file to trigger this vulnerability.

Frequently asked questions

What is CVE-2021-21867?: An unsafe deserialization vulnerability exists in the ObjectManager.plugin ObjectStream.ProfileByteArray functionality of CODESYS GmbH CODESYS Development System 3.5.16 and 3.5.17. A specially crafted file can lead to arbitrary command execution. An attacker can provide a malicious file to trigger this vulnerability.
How severe is CVE-2021-21867?: CVE-2021-21867 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-21867 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (74th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-21867?: CVE-2021-21867 primarily affects Codesys. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-21867?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-21867 published?: CVE-2021-21867 was published on 2021-08-18 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:codesys:codesys:3.5.16.0:*:*:*:*:*:*:*
cpe:2.3:a:codesys:codesys:3.5.17.0:*:*:*:*:*:*:*

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