CVE-2021-30809 in iOS
Summary
by MITRE • 10/28/2021
A use after free issue was addressed with improved memory management. This issue is fixed in Safari 15, tvOS 15, watchOS 8, iOS 15 and iPadOS 15. Processing maliciously crafted web content may lead to arbitrary code execution.
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Analysis
by VulDB Data Team • 05/22/2025
The vulnerability identified as CVE-2021-30809 represents a critical use-after-free condition that existed in Apple's web browser Safari and related operating systems. This memory safety issue stems from improper handling of memory allocation and deallocation processes within the browser's rendering engine. The flaw occurs when the application attempts to access memory locations that have already been freed, creating a scenario where malicious actors can manipulate the memory state to execute arbitrary code. Such vulnerabilities are particularly dangerous because they can be exploited remotely through web content without any user interaction beyond visiting a compromised website.
The technical implementation of this vulnerability aligns with CWE-416, which specifically addresses use-after-free conditions in software systems. When Safari processes maliciously crafted web content, the browser's memory management mechanisms fail to properly track object references, allowing freed memory blocks to be reallocated and subsequently accessed by attacker-controlled code. This memory corruption vulnerability can be leveraged to bypass modern exploit mitigation techniques such as address space layout randomization and data execution prevention. The flaw demonstrates a classic memory safety issue where the application's object lifecycle management breaks down during web page rendering operations, particularly when handling complex web content with embedded scripts or multimedia elements.
The operational impact of CVE-2021-30809 extends across multiple Apple platforms including iOS 15, iPadOS 15, watchOS 8, tvOS 15, and Safari 15, affecting a broad user base of mobile and desktop devices. Attackers can exploit this vulnerability by hosting malicious web content that triggers the memory corruption when loaded in Safari, potentially leading to full system compromise without requiring user interaction beyond navigation to the malicious site. The remote exploitation capability makes this vulnerability particularly dangerous in phishing campaigns or compromised websites where attackers can silently execute malicious code on target systems. This type of vulnerability directly maps to attack techniques described in the MITRE ATT&CK framework under T1059 for command and scripting interpreter and T1190 for exploitation of remote services.
Apple's fix for CVE-2021-30809 involved implementing enhanced memory management protocols and improved object reference tracking within Safari's web rendering engine. The security patch addresses the root cause by ensuring proper memory deallocation procedures and preventing access to freed memory blocks during web content processing. Organizations should prioritize immediate deployment of the affected software updates across all supported platforms to mitigate the risk of exploitation. Security teams should also implement network monitoring to detect potential exploitation attempts targeting this vulnerability and consider deploying web application firewalls to filter malicious content. The remediation process should include verification of patch deployment through automated inventory management systems to ensure complete coverage across all affected devices and operating system versions.