CVE-2021-1789
CVE-2021-1789 is a security flaw in Apple devices, the software on Apple’s iPhones, iPads and Macs. Attackers can run their own code on Apple devices. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 4 May 2022.[1]
Apple devices is in things households have, such as phones, computers, browsers and everyday apps, so the fix matters at home as much as at work. Fixed in version 14.4, 11.2, 7.3 and 14.0.
Description
CISA calls it a type confusion in Apple Multiple Products. In its words: “A type confusion issue affecting multiple Apple products allows processing of maliciously crafted web content, leading to arbitrary code execution.”[1]
The CVE record adds: “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.”[2]
The underlying weakness is type confusion (CWE-843), in MITRE’s list of common software weaknesses.
It scores 8.8 out of 10 on the Common Vulnerability Scoring System, which rates it high, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record lists these fixed versions: in each line, everything before the version shown is affected.[2]
| Product | Fixed in |
|---|---|
| iOS and iPadOS | 14.4 |
| macOS | 11.2 |
| macOS | 7.3 |
| macOS | 14.4 |
| macOS | 14.0 |
Every device with Apple devices needs the update.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 4 May 2022, 397 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 25 May 2022 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 14%. That’s in the top 4% of the flaws it scores.[4]
CISA assesses it as not automatable: each attack takes some work.
CISA doesn’t say who was attacked, or how.
Fix
Apple has published a fix or advice.[3] CISA’s required action: “Apply updates per vendor instructions.”[1]
- Update Apple devices now.On iPhone and iPad: Settings, General, Software Update. On a Mac: System Settings, General, Software Update. Install it on every Apple device in the house. Then turn on automatic updates, so the next fix arrives on its own.
- Check you’re on 14.4 or later.Fixed in version 14.4, 11.2, 7.3 and 14.0. Anything older is what attackers are going after.
- If there’s no update, stop using it.CISA’s advice when a flaw being used in attacks has no fix is to stop using the product until it does.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 8.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 14%.[4] |
See also
Other Apple devices flaws
- CVE-2026-86950: out-of-bounds write ·
- CVE-2025-43520: classic buffer overflow ·
- CVE-2025-43510: improper locking ·
- CVE-2025-31277: buffer overflow ·
- CVE-2023-43000: use-after-free ·
- CVE-2021-30952: integer overflow or wraparound ·
Other type confusion flaws
- CVE-2026-85046, Chrome and other Chromium browsers: type confusion ·
- CVE-2026-21519, Microsoft Windows: type confusion ·
- CVE-2025-13223, Chrome and other Chromium browsers: type confusion ·
- CVE-2025-10585, Chrome and other Chromium browsers: type confusion ·
- CVE-2025-6554, Chrome and other Chromium browsers: type confusion ·
Added the same day
- CVE-2019-8506, Apple devices: type confusion ·
- CVE-2014-4113, Microsoft Win32k: privilege escalation ·
- CVE-2014-0322, Microsoft Internet Explorer: use-after-free ·
- CVE-2014-0160, OpenSSL: information disclosure ·
Every Apple flaw on CISA’s list · Everything added in May 2022
References
- ^ Cybersecurity and Infrastructure Security Agency. “Apple Multiple Products Type Confusion Vulnerability”. Known Exploited Vulnerabilities Catalog, added 4 May 2022.
- ^ National Institute of Standards and Technology. “CVE-2021-1789 Detail”. National Vulnerability Database, published 2 Apr 2021.
- ^ Apple. Advisories and fixes: support.apple.com, support.apple.com, support.apple.com, support.apple.com, support.apple.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.140, percentile 96.5, 31 Oct 2026.
- CVE Program. “CVE-2021-1789”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.