The ongetmissingevents function in handlers/federation.py in Matrix Synapse before 0.31.1 has a security bug in the getmissing_events federation API where event visibility rules were not applied correctly.
{
"cpe": "cpe:2.3:a:matrix:synapse:*:*:*:*:*:*:*:*",
"source": [
"CPE_FIELD",
"REFERENCES"
],
"extracted_events": [
{
"introduced": "0"
},
{
"fixed": "0.31.1"
}
]
}