Cyber Resilience

CVE-2020-27950

Apple Watchos ≤ 5.3.9

CISA KEVActive ExploitationEUVD ExploitedPublic PoC
Published
08 December 2020
Modified
27 October 2025
KEV Added
03 November 2021
Patch / advisory
CVSS Score v3.1 5.5
Click a component to see what it means
Raw vectorCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
EPSS Score 0.17 97th percentile
Risk Priority 75 floored blend · peak EPSS

Summary

CVE-2020-27950 is a medium-severity Improper Initialization (CWE-665) vulnerability in Apple Watchos. Its CVSS base score is 5.5 (Medium).

Operationally, ranked in the top 3% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

A memory initialization issue tracked as CVE-2020-27950 affects the XNU kernel on multiple Apple platforms. The flaw, assigned CWE-665, permits a malicious application to disclose kernel memory and is resolved in macOS Big Sur 11.0.1, macOS Catalina 10.15.7 Supplemental Update, Security Update 2020-006 for High Sierra and Mojave, iOS 14.2 and iPadOS 14.2, iOS 12.4.9, and corresponding watchOS releases. The CVSS 5.5 vector reflects local attack complexity with no privileges required and user interaction needed for successful exploitation.

An attacker who can persuade a user to run a malicious application on an affected device may read kernel memory contents. The issue manifests through improper initialization of Mach message trailers, enabling controlled disclosure of sensitive kernel data without elevated privileges.

Apple security advisories HT211928, HT211929, and HT211931 direct administrators to install the listed operating-system updates. Public technical details and proof-of-concept material have been published via Full Disclosure and Packet Storm, confirming the memory-disclosure primitive in the kernel's Mach messaging code.

EU & UK References

Vulnerability Data

A memory initialization issue was addressed. This issue is fixed in macOS Big Sur 11.0.1, watchOS 7.1, iOS 12.4.9, watchOS 6.2.9, Security Update 2020-006 High Sierra, Security Update 2020-006 Mojave, iOS 14.2 and iPadOS 14.2, watchOS 5.3.9, macOS Catalina 10.15.7…

more

Supplemental Update, macOS Catalina 10.15.7 Update. A malicious application may be able to disclose kernel memory.

CWE(s)
KEV Date Added
03 November 2021

Related Threats

CVEs Like This One

CVE-2022-32894Same product: Apple Ipadosboth on KEV
CVE-2023-32434Same product: Apple Ipadosboth on KEV
CVE-2021-30807Same product: Apple Ipadosboth on KEV
CVE-2023-41990Same product: Apple Ipadosboth on KEV
CVE-2025-43200Same product: Apple Ipadosboth on KEV
CVE-2022-48618Same product: Apple Ipadosboth on KEV
CVE-2022-22675Same product: Apple Ipadosboth on KEV
CVE-2020-27930Same product: Apple Ipadosboth on KEV
CVE-2021-30665Same product: Apple Ipadosboth on KEV
CVE-2021-30883Same product: Apple Ipadosboth on KEV

Affected Assets

apple
ipados
≤ 14.2
apple
iphone os
≤ 12.4.9 · 14.0 — 14.2
apple
macos
≤ 10.15.7 · 11.0 — 11.0.1
apple
watchos
≤ 5.3.9 · 6.0 — 6.2.9 · 7.0 — 7.1

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

addresses: CWE-665

Ensures shared resources are explicitly initialized or cleared on allocation, preventing exposure of prior contents to new users or processes.

addresses: CWE-665

Mandates that every instance begins in a known (presumably clean) state, eliminating reliance on residual or uninitialized state left by prior executions.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly enforce proper resource initialization during coding and testing.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

finds

Security testing can detect uninitialized variables but does not itself enforce initialization practices.

prevents

Configuration management can enforce secure defaults and initialization settings but is not the primary control for code-level initialization.

prevents

Secure development life cycle mandates initialization checks and secure defaults that directly prevent improper resource initialization.

prevents

Secure system architecture and engineering principles require explicit initialization of resources and secure state management.

prevents

Secure coding standards explicitly forbid uninitialized variables and mandate proper resource initialization before use.

References