How severe is CVE-2021-1878?

CVE-2021-1878 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2021-1878 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-1878?

CVE-2021-1878 primarily affects Apple Mac Os X. In total, 28 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-1878?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-1878 published?

CVE-2021-1878 was published on 2021-09-08 and last updated on 2026-06-17.

CVE-2021-1878

CVE-2021-1878 is a medium-severity vulnerability in Apple Mac Os X with a CVSS 3.x base score of 6.5. 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-190.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 4.0
EPSS exploit prediction: 2% (76th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-190
Affected product: Apple Mac Os X
Published: 2021-09-08
Last modified: 2026-06-17

Description

An integer overflow was addressed with improved input validation. This issue is fixed in macOS Big Sur 11.3, Security Update 2021-002 Catalina, Security Update 2021-003 Mojave. An attacker in a privileged network position may be able to leak sensitive user information.

Frequently asked questions

What is CVE-2021-1878?: An integer overflow was addressed with improved input validation. This issue is fixed in macOS Big Sur 11.3, Security Update 2021-002 Catalina, Security Update 2021-003 Mojave. An attacker in a privileged network position may be able to leak sensitive user information.
How severe is CVE-2021-1878?: CVE-2021-1878 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2021-1878 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-1878?: CVE-2021-1878 primarily affects Apple Mac Os X. In total, 28 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-1878?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-1878 published?: CVE-2021-1878 was published on 2021-09-08 and last updated on 2026-06-17.

References

Affected products (28)

cpe:2.3:o:apple:mac_os_x:*:*:*:*:*:*:*:*
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:10.14.6:supplemental_update:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.14.6:supplemental_update_2:*:*:*:*:*:*
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: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:*:*:*:*:*:*
cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2021-001:*:*:*:*:*:*
cpe:2.3:o:apple:macos:*:*:*:*:*:*:*:*

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