CVE-2021-30952
CVE-2021-30952 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 5 Mar 2026.[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 8.3, 15.2 and 12.1.
Description
CISA calls it an integer overflow or wraparound in Apple Multiple Products. In its words: “Apple tvOS, macOS, Safari, iPadOS and watchOS contain an integer overflow or wraparound vulnerability due to the processing of maliciously crafted web content that may lead to arbitrary code execution.”[1]
The CVE record adds: “An integer overflow was addressed with improved input validation. This issue is fixed in tvOS 15.2, macOS Monterey 12.1, Safari 15.2, iOS 15.2 and iPadOS 15.2, watchOS 8.3. Processing maliciously crafted web content may lead to arbitrary code execution.”[2]
The underlying weakness is integer overflow (CWE-190), in MITRE’s list of common software weaknesses.
It scores 7.8 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 |
|---|---|
| watchOS | 8.3 |
| iOS and iPadOS | 15.2 |
| macOS | 12.1 |
| macOS | 15.2 |
Every device with Apple devices needs the update.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 5 Mar 2026, 1,654 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 26 Mar 2026 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 7%. That’s in the top 6% 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 mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.”[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 8.3 or later.Fixed in version 8.3, 15.2 and 12.1. 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 7.8.[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 7%.[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-2026-20700: multiple buffer overflow ·
Other integer overflow flaws
- CVE-2026-97229, GitLab Community Edition and Enterprise Edition: integer overflow or wraparound ·
- CVE-2025-48595, Android Framework: integer overflow ·
- CVE-2026-21385, Qualcomm Multiple Chipsets: memory corruption ·
- CVE-2018-14634, Linux Kernel: integer overflow ·
- CVE-2025-24985, Microsoft Windows: fast FAT file system driver integer overflow ·
Added the same day
- CVE-2023-43000, Apple devices: use-after-free ·
- CVE-2023-41974, Apple iOS and iPadOS: use-after-free ·
- CVE-2021-22681, Rockwell products: insufficient protected credentials ·
- CVE-2017-7921, Hikvision products: improper authentication ·
Every Apple flaw on CISA’s list · Everything added in March 2026
References
- ^ Cybersecurity and Infrastructure Security Agency. “Apple Multiple Products Integer Overflow or Wraparound Vulnerability”. Known Exploited Vulnerabilities Catalog, added 5 Mar 2026.
- ^ National Institute of Standards and Technology. “CVE-2021-30952 Detail”. National Vulnerability Database, published 24 Aug 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 0.070, percentile 94.1, 31 Oct 2026.
- CVE Program. “CVE-2021-30952”. 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.