How severe is CVE-2021-27388?

CVE-2021-27388 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-2021-27388 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (72nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-27388?

CVE-2021-27388 primarily affects Siemens Sinamics Sl150 Firmware. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-27388?

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-2021-27388 published?

CVE-2021-27388 was published on 2021-06-15 and last updated on 2026-06-17.

CVE-2021-27388

CVE-2021-27388 is a critical-severity vulnerability in Siemens Sinamics Sl150 Firmware 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-20.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (72nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Siemens Sinamics Sl150 Firmware
Published: 2021-06-15
Last modified: 2026-06-17

Description

SINAMICS medium voltage routable products are affected by a vulnerability in the Sm@rtServer component for remote access that could allow an unauthenticated attacker to cause a denial-of-service condition, and/or execution of limited configuration modifications and/or execution of limited control commands on the SINAMICS Medium Voltage Products, Remote Access (SINAMICS SL150: All versions, SINAMICS SM150: All versions, SINAMICS SM150i: All versions).

Frequently asked questions

What is CVE-2021-27388?: SINAMICS medium voltage routable products are affected by a vulnerability in the Sm@rtServer component for remote access that could allow an unauthenticated attacker to cause a denial-of-service condition, and/or execution of limited configuration modifications and/or execution of limited control commands on the SINAMICS Medium Voltage Products, Remote Access (SINAMICS SL150: All versions, SINAMICS SM150: All versions, SINAMICS SM150i: All versions).
How severe is CVE-2021-27388?: CVE-2021-27388 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-2021-27388 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (72nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-27388?: CVE-2021-27388 primarily affects Siemens Sinamics Sl150 Firmware. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-27388?: 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-2021-27388 published?: CVE-2021-27388 was published on 2021-06-15 and last updated on 2026-06-17.

References

https://us-cert.cisa.gov/ics/advisories/icsa-21-131-04

Affected products (3)

cpe:2.3:o:siemens:sinamics_sl150_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:sinamics_sm150_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:sinamics_sm150i_firmware:*:*:*:*:*:*:*:*

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