How severe is CVE-2021-33719?

CVE-2021-33719 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-33719 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (80th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-33719?

CVE-2021-33719 primarily affects Siemens Siprotec 5 With Cpu Variant Cp050. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-33719?

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

When was CVE-2021-33719 published?

CVE-2021-33719 was published on 2021-09-14 and last updated on 2026-06-17.

CVE-2021-33719

CVE-2021-33719 is a critical-severity vulnerability in Siemens Siprotec 5 With Cpu Variant Cp050 with a CVSS 3.x base score of 9.8. 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-120.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (80th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-120
Affected product: Siemens Siprotec 5 With Cpu Variant Cp050
Published: 2021-09-14
Last modified: 2026-06-17

Description

A vulnerability has been identified in SIPROTEC 5 relays with CPU variants CP050 (All versions < V8.80), SIPROTEC 5 relays with CPU variants CP100 (All versions < V8.80), SIPROTEC 5 relays with CPU variants CP300 (All versions < V8.80). Specially crafted packets sent to port 4443/tcp could cause a Denial-of-Service condition or potential remote code execution.

Frequently asked questions

What is CVE-2021-33719?: A vulnerability has been identified in SIPROTEC 5 relays with CPU variants CP050 (All versions < V8.80), SIPROTEC 5 relays with CPU variants CP100 (All versions < V8.80), SIPROTEC 5 relays with CPU variants CP300 (All versions < V8.80). Specially crafted packets sent to port 4443/tcp could cause a Denial-of-Service condition or potential remote code execution.
How severe is CVE-2021-33719?: CVE-2021-33719 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-33719 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (80th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-33719?: CVE-2021-33719 primarily affects Siemens Siprotec 5 With Cpu Variant Cp050. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-33719?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-33719 published?: CVE-2021-33719 was published on 2021-09-14 and last updated on 2026-06-17.

References

https://cert-portal.siemens.com/productcert/pdf/ssa-847986.pdf

Affected products (3)

cpe:2.3:o:siemens:siprotec_5_with_cpu_variant_cp050:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:siprotec_5_with_cpu_variant_cp100:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:siprotec_5_with_cpu_variant_cp300:*:*:*:*:*:*:*:*

More vulnerabilities in Siemens Siprotec 5 With Cpu Variant Cp050

CVE-2021-37206 — High (CVSS 7.5): A vulnerability has been identified in SIPROTEC 5 relays with CPU variants CP050 (All versions < V8.80), SIPROTEC 5…
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