How severe is CVE-2021-30856?

CVE-2021-30856 has a CVSS 3.x base score of 9.1, 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 none.

Is CVE-2021-30856 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (57th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-30856?

CVE-2021-30856 affects Apple Macos. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-30856?

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-2021-30856 published?

CVE-2021-30856 was published on 2021-08-24 and last updated on 2026-06-17.

CVE-2021-30856

CVE-2021-30856 is a critical-severity vulnerability in Apple Macos with a CVSS 3.x base score of 9.1. 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-863.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
CVSS v2: 5.8
EPSS exploit prediction: 1% (57th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-863
Affected product: Apple Macos
Published: 2021-08-24
Last modified: 2026-06-17

Description

This issue was addressed by adding a new Remote Login option for opting into Full Disk Access for Secure Shell sessions. This issue is fixed in macOS Big Sur 11.3. A malicious unsandboxed app on a system with Remote Login enabled may bypass Privacy preferences.

Frequently asked questions

What is CVE-2021-30856?: This issue was addressed by adding a new Remote Login option for opting into Full Disk Access for Secure Shell sessions. This issue is fixed in macOS Big Sur 11.3. A malicious unsandboxed app on a system with Remote Login enabled may bypass Privacy preferences.
How severe is CVE-2021-30856?: CVE-2021-30856 has a CVSS 3.x base score of 9.1, 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 none.
Is CVE-2021-30856 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (57th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-30856?: CVE-2021-30856 affects Apple Macos. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-30856?: 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-2021-30856 published?: CVE-2021-30856 was published on 2021-08-24 and last updated on 2026-06-17.

References

https://support.apple.com/en-us/HT212325

Affected products (1)

cpe:2.3:o:apple:macos:*:*:*:*:*:*:*:*

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