How severe is CVE-2021-40365?

CVE-2021-40365 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 none, integrity none, and availability high.

Is CVE-2021-40365 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-40365?

CVE-2021-40365 primarily affects Siemens Simatic S7-plcsim Advanced Firmware. In total, 96 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-40365?

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-2021-40365 published?

CVE-2021-40365 was published on 2022-12-13 and last updated on 2026-06-17.

CVE-2021-40365

CVE-2021-40365 is a high-severity vulnerability in Siemens Simatic S7-plcsim Advanced Firmware 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-20.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 1% (54th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Siemens Simatic S7-plcsim Advanced Firmware
Published: 2022-12-13
Last modified: 2026-06-17

Description

Affected devices don't process correctly certain special crafted packets sent to port 102/tcp, which could allow an attacker to cause a denial of service in the device.

Frequently asked questions

What is CVE-2021-40365?: Affected devices don't process correctly certain special crafted packets sent to port 102/tcp, which could allow an attacker to cause a denial of service in the device.
How severe is CVE-2021-40365?: CVE-2021-40365 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 none, integrity none, and availability high.
Is CVE-2021-40365 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-40365?: CVE-2021-40365 primarily affects Siemens Simatic S7-plcsim Advanced Firmware. In total, 96 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-40365?: 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-2021-40365 published?: CVE-2021-40365 was published on 2022-12-13 and last updated on 2026-06-17.

References

https://cert-portal.siemens.com/productcert/pdf/ssa-382653.pdf

Affected products (96)

cpe:2.3:o:siemens:simatic_s7-plcsim_advanced_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1200_cpu_1211c_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1200_cpu_1212c_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1200_cpu_1212fc_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1200_cpu_1214_fc_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1200_cpu_1214c_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1200_cpu_1214fc_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1200_cpu_1215_fc_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1200_cpu_1215c_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1200_cpu_1215fc_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1200_cpu_1217c_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1200_cpu_12_1211c_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1200_cpu_12_1212c_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1200_cpu_12_1212fc_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1200_cpu_12_1214c_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1200_cpu_12_1214fc_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1200_cpu_12_1215c_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1200_cpu_12_1215fc_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1200_cpu_12_1217c_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:siplus_s7-1200_cp_1243-1_rail_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:siplus_s7-1200_cp_1243-1_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1507s_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1507s_f_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1508s_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1508s_f_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1510sp_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1510sp-1_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1511-1_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1511-1_pn_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1511c_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1511c-1_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1511f-1_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1511f-1_pn_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1511t-1_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1511tf-1_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1512c_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1512c-1_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1512sp-1_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1512spf-1_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1513-1_firmware:*:*:*:*:*:*:*:*

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