CVE-2021-21203 in Chrome
Summary
by MITRE • 04/26/2021
Use after free in Blink in Google Chrome prior to 90.0.4430.72 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.
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Analysis
by VulDB Data Team • 04/30/2021
The vulnerability CVE-2021-21203 represents a critical use-after-free condition within the Blink rendering engine of Google Chrome, affecting versions prior to 90.0.4430.72. This flaw resides in the browser's core rendering component responsible for processing and displaying web content, making it a prime target for remote exploitation. The issue manifests when the browser processes specially crafted HTML pages that trigger improper memory management during object deallocation, creating opportunities for attackers to manipulate heap memory structures.
The technical implementation of this vulnerability involves the Blink engine's failure to properly validate memory references after objects have been freed from the heap. When a webpage contains maliciously constructed HTML elements or JavaScript code, the rendering engine may attempt to access memory locations that have already been deallocated, leading to heap corruption. This memory corruption can result in arbitrary code execution, as attackers can manipulate the freed memory to redirect program execution flow or inject malicious payloads. The vulnerability falls under CWE-416, which specifically addresses use-after-free conditions in software systems.
From an operational perspective, this vulnerability poses significant risks to end users who browse the internet without proper security measures. Remote attackers can exploit this flaw by hosting malicious web pages that trigger the vulnerable code path when loaded in affected Chrome versions. The attack surface is extensive since any webpage could potentially contain the malicious payload, making it particularly dangerous for users who visit untrusted websites or click on phishing links. The exploitation process typically requires no user interaction beyond visiting the compromised page, making it a serious concern for enterprise environments and individual users alike.
The impact of CVE-2021-21203 extends beyond simple browser compromise, as successful exploitation can lead to full system compromise through various attack vectors outlined in the MITRE ATT&CK framework. Attackers can leverage this vulnerability to establish persistent access, escalate privileges, or deploy additional malware. The heap corruption aspect of this vulnerability aligns with ATT&CK technique T1059 for command and script execution, as attackers can use the arbitrary code execution capabilities to run malicious commands. Organizations should prioritize patch management and browser updates to mitigate this risk, as the vulnerability has been addressed in Chrome version 90.0.4430.72 and subsequent releases. Security professionals should also implement network monitoring to detect potential exploitation attempts and maintain awareness of related vulnerabilities that may leverage similar memory corruption patterns.