How severe is CVE-2021-1834?

CVE-2021-1834 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-2021-1834 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (86th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-1834?

CVE-2021-1834 primarily affects Apple Mac Os X. In total, 42 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-1834?

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-2021-1834 published?

CVE-2021-1834 was published on 2021-09-08 and last updated on 2026-06-17.

CVE-2021-1834

CVE-2021-1834 is a critical-severity vulnerability in Apple Mac Os X 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-787.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 10.0
EPSS exploit prediction: 3% (86th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-787
Affected product: Apple Mac Os X
Published: 2021-09-08
Last modified: 2026-06-17

Description

An out-of-bounds write issue was addressed with improved bounds checking. This issue is fixed in macOS Big Sur 11.3, Security Update 2021-002 Catalina, Security Update 2021-003 Mojave. A malicious application may be able to execute arbitrary code with kernel privileges.

Frequently asked questions

What is CVE-2021-1834?: An out-of-bounds write issue was addressed with improved bounds checking. This issue is fixed in macOS Big Sur 11.3, Security Update 2021-002 Catalina, Security Update 2021-003 Mojave. A malicious application may be able to execute arbitrary code with kernel privileges.
How severe is CVE-2021-1834?: CVE-2021-1834 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-2021-1834 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (86th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-1834?: CVE-2021-1834 primarily affects Apple Mac Os X. In total, 42 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-1834?: 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-2021-1834 published?: CVE-2021-1834 was published on 2021-09-08 and last updated on 2026-06-17.

References

Affected products (42)

cpe:2.3:o:apple:mac_os_x:10.14:*:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.0:*:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.1:*:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.2:*:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.3:*:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.4:*:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.4:beta4:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.5:*:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.6:*:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.6:-:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.6:security_update_2019-001:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.6:security_update_2019-002:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.6:security_update_2019-004:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.6:security_update_2019-005:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.6:security_update_2019-006:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.6:security_update_2019-007:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.6:security_update_2020-001:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.6:security_update_2020-002:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.6:security_update_2020-003:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.6:security_update_2020-004:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.6:security_update_2020-005:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.6:security_update_2020-006:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.6:security_update_2020-007:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.6:security_update_2021-001:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.6:security_update_2021-002:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.15:*:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.15.1:*:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.15.2:*:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.15.3:*:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.15.4:*:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.15.5:*:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.15.6:*:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.15.6:-:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.15.6:supplemental_update:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.15.7:*:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.15.7:-:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2020:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2020-001:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2020-005:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2020-007:*:*:*:*:*:*

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