Cyber Resilience

CVE-2021-1871

CriticalCISA KEVActive ExploitationEUVD Exploited

Published: 02 April 2021

Published
02 April 2021
Modified
23 October 2025
KEV Added
03 November 2021
Patch
CVSS Score v3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.0048 65.7th percentile
Risk Priority 40 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2021-1871 is a critical-severity an unspecified weakness vulnerability in Apple Mac Os X. Its CVSS base score is 9.8 (Critical).

Operationally, ranked in the top 34.3% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog.

The strongest mitigations our analysis identified are NIST 800-53 SI-2 (Flaw Remediation) and SC-7 (Boundary Protection).

Deeper analysis

A logic issue addressed with improved restrictions affects multiple Apple operating systems, including versions of macOS prior to Big Sur 11.2, Catalina and Mojave prior to Security Update 2021-001, and iOS and iPadOS prior to 14.4. The flaw received a CVSS score of 9.8, reflecting network-accessible attack conditions with no required authentication or user interaction.

A remote attacker can exploit the vulnerability to achieve arbitrary code execution on an affected device. The attack requires only network connectivity and can fully compromise confidentiality, integrity, and availability of the target system.

Apple security updates for the listed platforms remediate the issue, and the vendor has stated awareness of reports indicating active exploitation in the wild. Additional distribution-specific advisories reference the same underlying component updates.

EU & UK References

Vulnerability details

A logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrary code…

more

execution. Apple is aware of a report that this issue may have been actively exploited..

CWE(s)
KEV Date Added
03 November 2021

Related Threats

No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.

Affected Assets

apple
ipados
≤ 14.4
apple
iphone os
≤ 14.4
apple
mac os x
10.15.7 · 10.15 — 10.15.7
apple
macos
11.0.1 — 11.2
debian
debian linux
10.0
fedoraproject
fedora
33

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

prevent

Directly requires timely installation of vendor security updates that remediate the logic flaw enabling remote code execution.

prevent

Boundary-protection mechanisms can restrict the network-accessible attack vector used to reach the vulnerable component without authentication.

detect

Continuous system monitoring can identify anomalous behavior or indicators associated with active exploitation of the RCE flaw.

References