CVE-2015-5122: Adobe Flash Player Use-After-Free Vulnerability

How it works

This issue is a use-after-free weakness (CWE-416) in Adobe Flash Player. In the DisplayObject class within the ActionScript 3 (AS3) implementation, memory that has already been freed can still be referenced. An attacker who can deliver crafted content that exercises this path may cause the player to use that stale memory, leading to arbitrary code execution or a denial-of-service condition. Public detail on exact trigger sequences is limited; treat any remote Flash content as a potential vector and confirm mechanics against the original vendor advisory.

Because Flash historically ran inside browsers and other host applications, successful abuse typically required the victim to load malicious SWF or embedded Flash content. The result is either full code execution in the context of the Flash process or a crash that disrupts availability.

Am I affected? How to find it in your systems

Adobe Flash Player is the affected product. It commonly appeared as a browser plugin, an embedded runtime in desktop applications, or a standalone player on endpoints and some legacy kiosks. Inventory every system that might still host Flash binaries or browser plugins.

• Search endpoints and application servers for Flash Player installers, OCX/DLL/plugin files, and registry or package-manager entries that reference Adobe Flash.
• Check browser configurations and enterprise software catalogs for any remaining Flash components; many organizations disabled or removed the plugin years ago, but residual copies can linger on older images.
• Because the product is end-of-life, any remaining installation should be treated as in-scope regardless of version; confirm exact build details only against historical vendor advisories if needed for documentation.
• Telemetry signs of exploitation are generic for this class: unexpected Flash process crashes, anomalous child processes spawned from browser or Flash hosts, or network callbacks immediately after loading untrusted SWF content. Review EDR and proxy logs for such patterns; no unique ransomware linkage is documented for this CVE.

How to remediate

The impacted product is end-of-life. CISA’s required action is to disconnect it if it is still in use. Remove Adobe Flash Player completely from all systems rather than attempting to patch. Uninstall via the operating-system package manager or Adobe’s removal tools, then verify that no plugin or runtime files remain.

• Prioritize internet-facing and user workstations where untrusted content could be loaded.
• Update golden images, software deployment baselines, and application whitelists so Flash cannot be reinstalled.
• For any business application that still embeds Flash, replace or rewrite the dependency; continued use of an EOL runtime leaves the use-after-free class exposed.

After removal, validate with file-system and process inventory that the component is gone. Confirm any residual configuration guidance against the last vendor advisory for the product.

If you can't patch immediately

Immediate removal is the correct long-term control. Until that is finished, apply compensating measures that reduce exposure for this weakness class:

• Network segmentation: isolate any host still running Flash from general user populations and from sensitive data stores.
• Disable the Flash plugin or ActiveX control in every browser and host application; block SWF MIME types and file extensions at web proxies and email gateways.
• Virtual patching / WAF rules that drop or sandbox requests containing Flash content can provide temporary protection; tune them to your environment and monitor for bypasses.
• Heighten monitoring on remaining Flash hosts: alert on process crashes, unusual module loads, and outbound connections after content render. Restrict execution with application control so only approved binaries run.

These steps only buy time; the definitive action remains full disconnection and removal of the end-of-life product.

If your data may have been exposed

Actively exploited vulnerabilities of this type have historically led to endpoint compromise and subsequent data theft. If Flash was present and untrusted content may have been loaded, assume possible code execution and perform standard incident response: isolate the host, collect volatile evidence, and hunt for persistence or lateral movement. Ransomware use specifically tied to this CVE is not documented, but any code-execution foothold warrants full investigation. As a quick additional check, you can run a free exposure scan of your email addresses against known breach data sets to see whether credentials or personal information have already appeared in public dumps.