Adobe Flash Player BitmapData Class Use-After-Free Remote Code Execution Vulnerability (CVE-2015-5123)
Executive & SecOps Summary
SECOPS ASSESSMENTAdobe Flash Player 13.x through 18.x and 11.x legacy versions on Windows, OS X, and Linux
Remote attackers can execute arbitrary code or cause a denial of service (memory corruption) via crafted Flash content
Since Adobe Flash Player has reached End-of-Life (EOL), the recommended mitigation is to completely uninstall Flash Player from all systems
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Adobe Flash Player is officially End-of-Life (EOL) and no longer receives security updates. The primary remediation is complete removal. On Windows, use the following PowerShell command to verify or enforce the removal of Flash Player via the official update.
# Check for the presence of the Windows Flash Removal Update (KB4577586)
$UpdateCheck = Get-HotFix -Id KB4577586 -ErrorAction SilentlyContinue
if ($null -eq $UpdateCheck) {
Write-Warning 'KB4577586 is not installed. Please deploy the Update for Removal of Adobe Flash Player.'
} else {
Write-Output 'Adobe Flash Player has been successfully decommissioned via KB4577586.'
}2. Temporary Workaround & Hardening Configuration
If immediate uninstallation is not feasible due to legacy dependencies, enforce strict browser policies to block Flash execution. Below is an example of disabling Flash via Chrome Enterprise Policy on Linux.
# Create Chrome policy directory and disable Flash execution
sudo mkdir -p /etc/opt/chrome/policies/managed
echo "{
'DefaultPluginsSetting': 2,
'PluginsAllowedForUrls':
}" | sudo tee /etc/opt/chrome/policies/managed/block_flash.json3. Log Audit & IoC Verification Commands
To identify residual Flash Player shared libraries or plugins on Linux endpoints, execute the following audit script.
# Scan for active or residual Flash Player shared objects and extract version strings
find /usr/lib/ /usr/lib64/ -name '*flashplayer*' -o -name 'libflashplayer.so' 2>/dev/null | while read -r plugin_path; do
echo 'Detected Flash Plugin: '$plugin_path
strings '$plugin_path' | grep -i 'LNX ' | head -n 1
doneBlock Kernel Privilege Escalation & Ransomware Payloads Before You Can Reboot
Protect unpatched Windows, Linux, and macOS workloads against in-memory exploitation and lateral movement with autonomous EDR.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2015-5123) is a critical Use-After-Free (UAF) flaw within the BitmapData class of the ActionScript 3 (AS3) implementation in Adobe Flash Player. The root cause lies in the engine's handling of user-defined overrides of the valueOf function, which allows an attacker to manipulate memory allocation and deallocation sequences during object processing.
2. Exploitation Mechanics & Attack Scenario
An attacker triggers the vulnerability by hosting a malicious Flash (.swf) file containing a BitmapData object. When a method of this object is called with an argument that overrides the valueOf method, the Flash Player engine executes the custom valueOf callback. Inside this callback, the attacker's code explicitly destroys or frees the underlying BitmapData memory buffer. Once the callback returns, the engine attempts to access the now-freed memory space (dangling pointer), resulting in a Use-After-Free condition that can be leveraged to hijack the execution flow and run arbitrary shellcode.
3. Infrastructure & Business Impact
This vulnerability was leaked during the Hacking Team breach in July 2015 and was actively exploited in the wild as a zero-day. Successful exploitation allows remote attackers to gain full system-level access to the host running the vulnerable Flash Player. In an enterprise environment, this poses a severe threat of initial entry, lateral movement, and potential ransomware deployment if legacy systems still run Flash-dependent applications.
Official Vendor Advisories & References
Use-after-free vulnerability in the BitmapData class in the ActionScript 3 (AS3) implementation in Adobe Flash Player 13.x through 13.0.0.302 on Windows and OS X, 14.x through 18.0.0.203 on Windows and OS X, 11.x through 11.2.202.481 on Linux, and 12.x through 18.0.0.204 on Linux Chrome installations allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via crafted Flash content that overrides a valueOf function, as exploited in the wild in July 2015.
Frequently Asked SecOps Questions (CVE-2015-5123)
FAQQ1. How critical is CVE-2015-5123 and is it actively exploited in the wild?
CVE-2015-5123 is rated CVSS 9.8 (CRITICAL) with a 30-day EPSS exploitation probability of 18.8%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2015-5123?
Primary impacted vendors include adobe across flash_player. Scope summary: Adobe Flash Player 13.x through 13.0.0.302 and 14.x through 18.0.0.203 on Windows/OS X, 11.x through 11.2.202.481 on Linux, and 12.x through 18.0.0.204 on Linux Chrome
Q3. What temporary mitigations or workarounds exist for CVE-2015-5123 before patching?
[Mitigation] Since Adobe Flash Player has reached End-of-Life (EOL), the recommended mitigation is to completely uninstall Flash Player from all systems Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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