CVE-2021-30983
Apple iOS and iPadOS Buffer Overflow Vulnerability
Description
CVE-2021-30983 is a buffer overflow vulnerability in Apple iOS and iPadOS that could allow a malicious application to execute arbitrary code with kernel privileges. The flaw exists in a kernel component where insufficient bounds checking on buffer operations enables an attacker to write beyond allocated memory boundaries, potentially corrupting kernel data structures and achieving full device compromise. CISA has added CVE-2021-30983 to its Known Exploited Vulnerabilities catalog, confirming active exploitation in the wild. With an EPSS score of 0.68% (71.3rd percentile), this vulnerability is associated with targeted attacks against Apple mobile devices.
KEV Information
CVSS Score
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:HOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| apple | ipados | < 15.2 |
| apple | iphone os | < 15.2 |
Multiple CVSS Assessments
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
References
- https://support.apple.com/en-us/HT212976(Release Notes, Vendor Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-30983(US Government Resource)
Weakness Type
CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
CVE-2021-30983 is a classic buffer overflow in an Apple iOS and iPadOS kernel component, where the system copies data into a fixed-size buffer without properly verifying that the input data fits within the allocated space. This allows an attacker-controlled application to overflow the buffer and overwrite adjacent kernel memory, enabling privilege escalation from application context to full kernel execution.
Learn more: CWE-120 — Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
Impact Analysis
CVE-2021-30983 enables kernel-level code execution on Apple iOS and iPadOS devices, which represents the highest level of privilege available on the platform. The vulnerability requires a locally installed malicious application as the attack vector, meaning the attacker needs some initial foothold on the device. Once the buffer overflow is exploited to achieve kernel code execution, the attacker bypasses all application sandboxing, data protection mechanisms, and security boundaries enforced by the operating system. Confidentiality is completely compromised as kernel access provides unrestricted access to all device data including encrypted content; integrity is fully at risk as the attacker can modify any system component; and availability can be disrupted through persistent modifications. The EPSS score of 0.68% (71.3rd percentile) suggests targeted exploitation rather than mass campaigns, consistent with the sophisticated nature of iOS kernel exploits.
Exploit Maturity
CISA has confirmed active exploitation of CVE-2021-30983 in the wild by adding it to the Known Exploited Vulnerabilities catalog on June 27, 2022, with a remediation deadline of July 18, 2022. iOS kernel vulnerabilities are extremely valuable in the exploit market and are typically used in targeted surveillance campaigns against high-value individuals. With an EPSS score of 0.68% (71.3rd percentile), exploitation is not widespread but is confirmed to be used in targeted operations. The buffer overflow in the kernel provides the privilege escalation component needed to deploy persistent surveillance tools on compromised iOS devices.
Remediation
- Update all Apple iOS and iPadOS devices: Install iOS 15.2 and iPadOS 15.2 or later, which contain the fix for CVE-2021-30983.
- Enable automatic security updates: Configure all Apple devices to automatically install security updates to minimize the exposure window for kernel-level vulnerabilities.
- Implement mobile device management restrictions: Use MDM policies to restrict the installation of applications from untrusted sources, reducing the risk of deploying a malicious application that could exploit this vulnerability.
- Enable Lockdown Mode for high-risk users: For individuals at elevated risk of targeted surveillance, Apple's Lockdown Mode provides additional protections that reduce the kernel attack surface.
- Monitor for unusual device behavior: Watch for indicators of compromise such as unexpected battery drain, unusual data usage, or device overheating that may signal kernel-level exploitation and surveillance tool deployment.
Technical Details
CVE-2021-30983 is a buffer overflow vulnerability in the Apple iOS and iPadOS kernel. The flaw exists in a kernel component where a buffer copy operation does not properly validate the size of the input data against the size of the destination buffer. When a malicious application triggers the vulnerable code path with oversized input, the resulting buffer overflow writes beyond the allocated memory region into adjacent kernel memory. By carefully controlling the overflow data, an attacker can corrupt kernel data structures, including function pointers or process credential structures, to achieve arbitrary code execution at the kernel privilege level. The local attack vector through a malicious application means the exploit typically requires either a prior remote code execution vulnerability or social engineering to install the attacking application. iOS kernel buffer overflows are among the most technically sophisticated and valuable exploit types due to the extensive mitigations present in modern Apple platforms.
Frequently Asked Questions
Is CVE-2021-30983 being actively exploited?
Yes. CISA has confirmed active exploitation of CVE-2021-30983 by adding it to the Known Exploited Vulnerabilities catalog. iOS kernel vulnerabilities are typically used in targeted surveillance campaigns against high-value individuals. Update to iOS 15.2 or later immediately.
What products are affected by CVE-2021-30983?
CVE-2021-30983 affects Apple iOS and iPadOS. Devices running versions prior to iOS 15.2 and iPadOS 15.2 are vulnerable. All iPhones and iPads should be updated to the latest available firmware.
How do I fix CVE-2021-30983?
Update all Apple iOS and iPadOS devices to version 15.2 or later. Enable automatic security updates and implement MDM restrictions on application installation. For high-risk users, enable Lockdown Mode.
How severe is CVE-2021-30983?
CVE-2021-30983 is a high-severity kernel buffer overflow with an EPSS score of 0.68% (71.3rd percentile) and confirmed active exploitation. The vulnerability enables kernel-level code execution, providing complete control over the affected iOS or iPadOS device. While exploitation requires a local application, the kernel-level impact makes this a critical patching priority.
Need Help With Vulnerability Management?
Our security experts can help you prioritize and remediate vulnerabilities effectively.