This indicates an attack attempt to exploit a Security Bypass vulnerability in Adobe Flash Player.
The vulnerability is due to an error when the vulnerable software handles a maliciously crafted HTTP Request. A remote attacker may be able to exploit this to bypass security mechanism of the application, via a crafted HTTP request.
Adobe Flash Player Desktop Runtime 22.214.171.124 on Windows and Macintosh
Adobe Flash Player Extended Support Release 126.96.36.1996 on Windows and Macintosh
Adobe Flash Player for Google Chrome 188.8.131.52 on Windows, Macintosh, Linux and ChromeOS
Adobe Flash Player for Microsoft Edge and Internet Explorer 11 184.108.40.206 on Windows 10 and 8.1
Adobe Flash Player for Linux 220.127.116.112 on Linux
Security Bypass: Remote attackers can bypass security mechanism of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.