CVE-2020-3757 Overview
CVE-2020-3757 is a type confusion vulnerability affecting Adobe Flash Player versions 32.0.0.321 and earlier across multiple platforms. This memory corruption flaw allows attackers to execute arbitrary code on vulnerable systems when a user visits a malicious website or opens a specially crafted Flash content. The vulnerability stems from improper handling of object types during runtime operations, enabling attackers to manipulate memory in unexpected ways.
Critical Impact
Successful exploitation of this type confusion vulnerability could allow remote attackers to execute arbitrary code in the context of the current user, potentially leading to complete system compromise, data theft, or installation of malware.
Affected Products
- Adobe Flash Player versions up to 32.0.0.321 (Desktop Runtime for Windows, macOS, Linux)
- Adobe Flash Player versions up to 32.0.0.314 (for Google Chrome)
- Adobe Flash Player versions up to 32.0.0.321 (for Microsoft Edge and Internet Explorer 11)
- Red Hat Enterprise Linux Desktop 6.0
- Red Hat Enterprise Linux Server 6.0
- Red Hat Enterprise Linux Workstation 6.0
Discovery Timeline
- February 13, 2020 - CVE-2020-3757 published to NVD
- November 21, 2024 - Last updated in NVD database
Technical Details for CVE-2020-3757
Vulnerability Analysis
This type confusion vulnerability (CWE-843) occurs when Adobe Flash Player processes specially crafted content that causes the application to misinterpret the type of an object. Type confusion vulnerabilities are particularly dangerous in Flash Player due to its complex ActionScript virtual machine, which handles numerous object types during execution.
When the Flash Player runtime incorrectly interprets an object as a different type than intended, it may access memory regions or execute code paths that were never designed for that data structure. This memory access confusion can be leveraged by attackers to achieve arbitrary code execution on the target system.
The attack requires user interaction—specifically, the victim must navigate to a malicious web page or open a crafted Flash file. However, given Flash's historical ubiquity in web browsers, this attack surface was significant at the time of disclosure.
Root Cause
The root cause lies in Flash Player's ActionScript bytecode interpreter, which fails to properly validate object types during certain runtime operations. When processing malformed SWF content, the interpreter may treat an attacker-controlled object as a trusted internal type, leading to memory corruption.
Type confusion vulnerabilities typically arise from insufficient type checking in object-oriented environments, where polymorphism and dynamic dispatch mechanisms can be abused. In Flash Player's case, the ActionScript Virtual Machine (AVM2) does not adequately verify type consistency during object operations.
Attack Vector
The attack is network-based and requires user interaction to trigger. An attacker can exploit this vulnerability through several vectors:
- Malicious Web Pages: Embedding crafted Flash content in a web page that victims are lured to visit
- Malicious Email Attachments: Sending SWF files or HTML documents with embedded Flash content
- Compromised Advertisements: Injecting malicious Flash content into ad networks (malvertising)
The attacker crafts a malicious SWF file that triggers the type confusion during parsing or execution. When the victim's Flash Player processes this content, the type confusion allows the attacker to manipulate memory and redirect code execution to attacker-controlled shellcode. The attacker would typically chain this with additional exploitation techniques such as heap spraying to achieve reliable code execution.
Detection Methods for CVE-2020-3757
Indicators of Compromise
- Unexpected Flash Player crashes or error messages when browsing websites
- Unusual network connections originating from browser processes after viewing Flash content
- Suspicious SWF files in browser cache or temporary directories
- Anomalous process spawning from browser or Flash Player processes
Detection Strategies
- Monitor for abnormal memory allocation patterns associated with Flash Player processes
- Implement network-based detection for known malicious SWF file signatures
- Deploy endpoint detection and response (EDR) solutions to identify exploitation attempts
- Use behavioral analysis to detect post-exploitation activities such as shellcode execution
Monitoring Recommendations
- Enable detailed logging for browser plugins and Flash Player activity
- Monitor process creation events for child processes spawned by Flash Player
- Implement file integrity monitoring for Flash Player installation directories
- Configure SIEM rules to alert on Flash Player-related anomalies across the enterprise
How to Mitigate CVE-2020-3757
Immediate Actions Required
- Update Adobe Flash Player to version 32.0.0.330 or later immediately
- Consider disabling Flash Player entirely given Adobe's end-of-life announcement
- Enable click-to-play settings for Flash content in all browsers
- Remove Flash Player from systems where it is not strictly required
- Apply vendor patches from Red Hat and other affected operating system vendors
Patch Information
Adobe has released security bulletin APSB20-06 addressing this vulnerability. Users should update to Flash Player version 32.0.0.330 or later. Red Hat has also issued RHSA-2020:0513 for affected Enterprise Linux distributions. Gentoo Linux users should refer to GLSA 202003-61 for distribution-specific guidance.
Note: Adobe Flash Player reached end-of-life on December 31, 2020, and is no longer supported. Organizations should prioritize complete removal of Flash Player from their environments.
Workarounds
- Disable Adobe Flash Player in browser settings until patches can be applied
- Configure browsers to prompt before running Flash content (click-to-play)
- Use browser extensions that block Flash content by default
- Implement network-level filtering to block SWF file downloads from untrusted sources
- Deploy application whitelisting to prevent unauthorized Flash content execution
# Configuration example - Disable Flash in Chrome via Group Policy
# Windows Registry configuration to disable Flash Player
reg add "HKLM\SOFTWARE\Policies\Google\Chrome\PluginsAllowedForUrls" /v "1" /t REG_SZ /d "" /f
reg add "HKLM\SOFTWARE\Policies\Google\Chrome" /v "DefaultPluginsSetting" /t REG_DWORD /d 2 /f
# For complete Flash removal (recommended)
# Windows: Uninstall via Programs and Features
# Linux: sudo yum remove flash-plugin (RHEL/CentOS)
# macOS: Delete /Library/Internet Plug-Ins/Flash Player.plugin
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
