How severe is CVE-2021-43928?

CVE-2021-43928 has a CVSS 3.x base score of 9.9, rated critical severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-43928 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (77th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-43928?

CVE-2021-43928 affects Synology Mail Station. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-43928?

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-2021-43928 published?

CVE-2021-43928 was published on 2022-02-07 and last updated on 2026-06-17.

CVE-2021-43928

CVE-2021-43928 is a critical-severity vulnerability in Synology Mail Station with a CVSS 3.x base score of 9.9. 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-78.

Key facts

Severity: Critical (CVSS 3.x base score 9.9)
CVSS v2: 6.5
EPSS exploit prediction: 2% (77th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-78
Affected product: Synology Mail Station
Published: 2022-02-07
Last modified: 2026-06-17

Description

Improper neutralization of special elements used in an OS command ('OS Command Injection') vulnerability in mail sending and receiving component in Synology Mail Station before 20211105-10315 allows remote authenticated users to execute arbitrary commands via unspecified vectors.

Frequently asked questions

What is CVE-2021-43928?: Improper neutralization of special elements used in an OS command ('OS Command Injection') vulnerability in mail sending and receiving component in Synology Mail Station before 20211105-10315 allows remote authenticated users to execute arbitrary commands via unspecified vectors.
How severe is CVE-2021-43928?: CVE-2021-43928 has a CVSS 3.x base score of 9.9, rated critical severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-43928 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (77th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-43928?: CVE-2021-43928 affects Synology Mail Station. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-43928?: 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-2021-43928 published?: CVE-2021-43928 was published on 2022-02-07 and last updated on 2026-06-17.

References

https://www.synology.com/security/advisory/Synology_SA_21_28

Affected products (1)

cpe:2.3:a:synology:mail_station:*:*:*:*:*:*:*:*

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