Fastd Project: >> Fastd >> 0.5 Security Vulnerabilities
fastd is a VPN daemon which tunnels IP packets and Ethernet frames over UDP. When receiving a data packet from an unknown IP address/port combination, fastd will assume that one of its connected peers has moved to a new address and initiate a reconnect by sending a handshake packet. This "fast reconnect" avoids having to wait for a session timeout (up to ~90s) until a new connection is established. Even a 1-byte UDP packet just containing the fastd packet type header can trigger a much larger handshake packet (~150 bytes of UDP payload). Including IPv4 and UDP headers, the resulting amplification factor is roughly 12-13. By sending data packets with a spoofed source address to fastd instances reachable on the internet, this amplification of UDP traffic might be used to facilitate a Distributed Denial of Service attack. This vulnerability is fixed in v23.
CVSS Score
7.5
EPSS Score
0.008
Published
2025-01-27
receive.c in fastd before v21 allows denial of service (assertion failure) when receiving packets with an invalid type code.
CVSS Score
7.5
EPSS Score
0.011
Published
2020-10-22