How severe is CVE-2021-36765?

CVE-2021-36765 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2021-36765 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (58th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-36765?

CVE-2021-36765 affects Codesys Ethernetip. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-36765?

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-2021-36765 published?

CVE-2021-36765 was published on 2021-08-04 and last updated on 2026-06-17.

CVE-2021-36765

CVE-2021-36765 is a high-severity vulnerability in Codesys Ethernetip with a CVSS 3.x base score of 7.5. 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-476.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 1% (58th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-476
Affected product: Codesys Ethernetip
Published: 2021-08-04
Last modified: 2026-06-17

Description

In CODESYS EtherNetIP before 4.1.0.0, specific EtherNet/IP requests may cause a null pointer dereference in the downloaded vulnerable EtherNet/IP stack that is executed by the CODESYS Control runtime system.

Frequently asked questions

What is CVE-2021-36765?: In CODESYS EtherNetIP before 4.1.0.0, specific EtherNet/IP requests may cause a null pointer dereference in the downloaded vulnerable EtherNet/IP stack that is executed by the CODESYS Control runtime system.
How severe is CVE-2021-36765?: CVE-2021-36765 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2021-36765 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (58th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-36765?: CVE-2021-36765 affects Codesys Ethernetip. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-36765?: 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-2021-36765 published?: CVE-2021-36765 was published on 2021-08-04 and last updated on 2026-06-17.

References

https://customers.codesys.com/index.php?eID=dumpFile&t=f&f=16806&token=3b0c51de5a6e35bccbb413ddaaa56551ca5490f6&download=

Affected products (1)

cpe:2.3:a:codesys:ethernetip:*:*:*:*:*:*:*:*

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