CVE-2021-30657
CVE-2021-30657 is a security flaw in Apple macOS, the operating system on Macs. Attackers are using a flaw in Apple macOS that its maker hasn't described in detail. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 3 Nov 2021.[1]
Apple macOS 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 11.3 and 2021 of macOS.
Description
CISA calls it an unspecified in Apple macOS. In its words: “Apple macOS contains an unspecified logic issue in System Preferences that may allow a malicious application to bypass Gatekeeper checks.”[1]
The CVE record adds: “A logic issue was addressed with improved state management. This issue is fixed in macOS Big Sur 11.3, Security Update 2021-002 Catalina. A malicious application may bypass Gatekeeper checks. Apple is aware of a report that this issue may have been actively exploited..”[2]
The underlying weakness is missing authorization (CWE-862), in MITRE’s list of common software weaknesses.
It scores 5.5 out of 10 on the Common Vulnerability Scoring System, which rates it medium, 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 |
|---|---|
| macOS | 11.3 |
| macOS | 2021 |
Every device with Apple macOS needs the update.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 3 Nov 2021, 56 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 17 Nov 2021 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 69%. That’s in the top 1% 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 macOS 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 11.3 or later.Fixed in version 11.3 and 2021 of macOS. 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 5.5.[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 69%.[4] |
See also
Other Apple macOS flaws
- CVE-2026-65400: improper authentication ·
- CVE-2019-8526: use-after-free ·
- CVE-2022-22675: out-of-bounds write ·
- CVE-2022-22674: out-of-bounds read ·
- CVE-2021-30713: unspecified ·
Other Apple flaws
- CVE-2026-86950, Apple devices: out-of-bounds write ·
- CVE-2025-43520, Apple devices: classic buffer overflow ·
- CVE-2025-43510, Apple devices: improper locking ·
- CVE-2025-31277, Apple devices: buffer overflow ·
- CVE-2023-43000, Apple devices: use-after-free ·
Other missing authorization flaws
- CVE-2024-57726, SimpleHelp: missing authorization ·
- CVE-2023-52163, Digiever DS-2105 Pro: missing authorization ·
- CVE-2025-40602, SonicWall SMA1000 appliance: sMA1000 missing authorization ·
- CVE-2025-6205, Dassault Systèmes DELMIA Apriso: missing authorization ·
- CVE-2025-20362, Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense: secure firewall adaptive security (ASA) appliance and secure firewall threat defense (FTD) missing authorization ·
Added the same day
- CVE-2021-42258, BQE BillQuick Web Suite: SQL injection ·
- CVE-2021-42013, Apache HTTP Server: path traversal ·
- CVE-2021-41773, Apache HTTP Server: path traversal ·
- CVE-2021-40539, Zoho ManageEngine: aDSelfService plus authentication bypass ·
- CVE-2021-40444, Microsoft MSHTML: remote code execution ·
Every Apple flaw on CISA’s list · Everything added in November 2021
References
- ^ Cybersecurity and Infrastructure Security Agency. “Apple macOS Unspecified Vulnerability”. Known Exploited Vulnerabilities Catalog, added 3 Nov 2021.
- ^ National Institute of Standards and Technology. “CVE-2021-30657 Detail”. National Vulnerability Database, published 8 Sep 2021.
- ^ Apple. Advisories and fixes: support.apple.com, support.apple.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.685, percentile 99.3, 31 Oct 2026.
- CVE Program. “CVE-2021-30657”. 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.