Apple watchOS up to 8.1.1 Kernel race condition

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
7.5	$0-$5k	0.00

Summaryinfo

A vulnerability was found in Apple watchOS up to 8.1.1. It has been classified as critical. This affects an unknown function of the component Kernel. This manipulation causes race condition. This vulnerability is registered as CVE-2021-30955. The attack needs to be launched locally. No exploit is available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability classified as critical was found in Apple watchOS up to 8.1.1 (Smartwatch Operating System). Affected by this vulnerability is an unknown code block of the component Kernel. The manipulation with an unknown input leads to a race condition vulnerability. The CWE definition for the vulnerability is CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. As an impact it is known to affect confidentiality, integrity, and availability.

The weakness was published 12/13/2021 by Zweig as HT212975 as confirmed advisory (Website). It is possible to read the advisory at support.apple.com. This vulnerability is known as CVE-2021-30955. The technical details are unknown and an exploit is not publicly available. The advisory points out:

A malicious application may be able to execute arbitrary code with kernel privileges

Upgrading to version 8.3 eliminates this vulnerability. A possible mitigation has been published immediately after the disclosure of the vulnerability. The advisory contains the following remark:

A race condition was addressed with improved state handling.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2026-0631). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

Apple macOS

Productinfo

Type

Smartwatch Operating System

Vendor

Apple

Name

watchOS

Version

License

commercial

Website

Vendor: https://www.apple.com/

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.8
VulDB Meta Temp Score: 7.5

VulDB Base Score: 7.8
VulDB Temp Score: 7.5
VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv2info

AV	AC	Au	C	I	A
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💳	💳	💳	💳	💳	💳
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Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

Exploitinginfo

Class: Race condition
CWE: CWE-362
CAPEC: 🔍
ATT&CK: 🔍

Physical: Partially
Local: Yes
Remote: No

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

Reaction Time: 🔍
0-Day Time: 🔍
Exposure Time: 🔍

Upgrade: watchOS 8.3

Timelineinfo

04/13/2021 🔍
12/13/2021 +244 days 🔍
12/13/2021 +0 days 🔍
12/17/2021 +4 days 🔍
03/07/2026 +1541 days 🔍

Sourcesinfo

Vendor: apple.com

Advisory: HT212975
Researcher: Zweig
Status: Confirmed

CVE: CVE-2021-30955 (🔍)
GCVE (CVE): GCVE-0-2021-30955
GCVE (VulDB): GCVE-100-188515
CERT Bund: WID-SEC-2026-0631 - Apple macOS: Mehrere Schwachstellen

Entryinfo

Created: 12/17/2021 16:02
Updated: 03/07/2026 19:32
Changes: 12/17/2021 16:02 (19), 12/17/2021 16:05 (27), 12/23/2021 06:22 (1), 03/07/2026 19:32 (21)
Complete: 🔍
Cache ID: 216::103

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.