A HTTP/2 implementation built using any version of the Python priority library prior to version 1.2.0 could be targeted by a malicious peer by having that peer assign priority information for every possible HTTP/2 stream ID. The priority tree would happily continue to store the priority information for each stream, and would therefore allocate unbounded amounts of memory. Attempting to actually use a tree like this would also cause extremely high CPU usage to maintain the tree.
{
"versions": [
{
"introduced": "0"
},
{
"last_affected": "1.0.0"
},
{
"introduced": "0"
},
{
"last_affected": "1.1.0"
},
{
"introduced": "0"
},
{
"last_affected": "1.1.1"
}
]
}