CVE-2020-27950
Apple Watchos ≤ 5.3.9
Raw vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:NCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
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
- 🇪🇺 ENISA EUVD: EUVD-2020-20443
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
Affected Assets
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.
Ensures shared resources are explicitly initialized or cleared on allocation, preventing exposure of prior contents to new users or processes.
Mandates that every instance begins in a known (presumably clean) state, eliminating reliance on residual or uninitialized state left by prior executions.
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.
A.8.25 mandates security requirements, checkpoints, secure coding, testing and developer capability in the SDLC which reaches improper initialization as a design/coding defect, but leaves a bounded remainder (e.g. initialization of third-party components or libraries chosen in procurement, and post-deployment configuration defaults).
A.8.27 mandates security-by-design principles (least privilege, default-deny, fail-securely, distrust-external-input, hardening) plus explicit design reviews that can catch and block many uninitialized-resource cases before they ship, but leaves a bounded remainder (e.g. vendor libraries, runtime-initialization bugs, or post-review code changes) that can still be present and exploitable.
Secure coding standards explicitly forbid uninitialized variables and mandate proper resource initialization before use.
Security testing can detect uninitialized variables but does not itself enforce initialization practices.
defining, enforcing, and monitoring secure configuration templates (including defaults, disabled services, changed vendor passwords, minimized privileges) directly stops most improper-initialization cases from being exploitable; the bounded remainder is initialization logic inside custom application code that no configuration template reaches
Hardening callouts derived
DISA STIG baselines are authored against specific weaknesses. Where this CVE cites a broad weakness class, the mapping is not asserted at that abstraction (owner ruling, 2026-09-25: grade only at Base and below), so no rule is shown here rather than a rule shown against the wrong grain.
- No fine-grained STIG row for CWE-665, a class-level weakness. Rules are authored against its narrower children: CWE-770.