Apple watchOS up to 8.1.1 ImageIO out-of-bounds

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.
6.0	$0-$5k	0.00

Summaryinfo

A vulnerability described as critical has been identified in Apple watchOS up to 8.1.1. Affected by this issue is some unknown functionality of the component ImageIO. The manipulation results in out-of-bounds. This vulnerability was named CVE-2021-30939. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability, which was classified as critical, was found in Apple watchOS up to 8.1.1 (Smartwatch Operating System). Affected is an unknown code block of the component ImageIO. The manipulation with an unknown input leads to a out-of-bounds vulnerability. CWE is classifying the issue as CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. This is going to have an impact on confidentiality, integrity, and availability.

The weakness was presented 12/13/2021 by Rui Yang and Xingwei Lin as HT212975 as confirmed advisory (Website). The advisory is shared for download at support.apple.com. This vulnerability is traded as CVE-2021-30939. Successful exploitation requires user interaction by the victim. There are neither technical details nor an exploit publicly available. The advisory points out:

Processing a maliciously crafted image may lead to arbitrary code execution

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:

An out-of-bounds read was addressed with improved bounds checking.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2026-0631). Once again VulDB remains the best source 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: 6.3
VulDB Meta Temp Score: 6.0

VulDB Base Score: 6.3
VulDB Temp Score: 6.0
VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

Exploitinginfo

Class: Out-of-bounds
CWE: CWE-125 / CWE-119
CAPEC: 🔍
ATT&CK: 🔍

Physical: No
Local: No
Remote: Yes

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: Rui Yang, Xingwei Lin
Status: Confirmed

CVE: CVE-2021-30939 (🔍)
GCVE (CVE): GCVE-0-2021-30939
GCVE (VulDB): GCVE-100-188508
CERT Bund: WID-SEC-2026-0631 - Apple macOS: Mehrere Schwachstellen

Entryinfo

Created: 12/17/2021 15:59
Updated: 03/07/2026 10:12
Changes: 12/17/2021 15:59 (19), 12/17/2021 16:02 (27), 12/22/2021 20:43 (1), 03/07/2026 10:12 (21)
Complete: 🔍
Cache ID: 216::103