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.
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.
https://blog.torproject.org/node/2041 https://gitlab.torproject.org/tpo/core/tor/-/issues/40391 https://gitlab.torproject.org/tpo/core/tor/-/commit/4c06c619faceb5d158a725d97fda45cadb2cf9c9
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