CVE-2021-34549 log

A security issue has been found in Tor before version 0.4.5.9 that could be exploited for a hashtable-based CPU denial-of-service attack against relays. Previously a naive unkeyed hash function to look up circuits in a circuitmux object was used. An attacker could exploit this to construct circuits with chosen circuit IDs, to create collisions and make the hash table inefficient. Now a SipHash construction is used instead.