CVE-2021-39283: 
NixOS vulnerability analysis and mitigation

The vulnerability (CVE-2021-39283) affects Live555 through version 1.08, specifically in the liveMedia/FramedSource.cpp component. The issue was discovered and disclosed on August 18, 2021, where an assertion failure and application exit could be triggered via multiple SETUP and PLAY commands (CVE Mitre).

The vulnerability occurs in the liveMedia/FramedSource.cpp file where an assertion violation can be triggered when sending multiple SETUP and PLAY commands. When triggered, the system outputs 'FramedSource[0x610000000440]::getNextFrame(): attempting to read more than once at the same time!' and aborts execution. The vulnerability has been assigned a CVSS 3.1 score of 5.5 (Medium), with attack vector being Local, attack complexity Low, requiring no privileges but user interaction, and affecting only availability (Ubuntu Security).

The primary impact of this vulnerability is on system availability. When successfully exploited, it causes an assertion failure that leads to application exit, effectively creating a denial of service condition. This affects systems running Live555 streaming media server through version 1.08 (Live Devel).

The issue was addressed in Live555 changelog version 2021.08.13. Users should upgrade to this or later versions to mitigate the vulnerability. The fix specifically addresses the assertion violation in the FramedSource.cpp component (Live555 Changelog).