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.
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Tue, 28 Jan 2025 16:15:00 +0000
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Mon, 27 Jan 2025 17:45:00 +0000
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Description | 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. | |
Title | UDP traffic amplification via fastd's fast reconnect feature | |
Weaknesses | CWE-405 | |
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cvssV4_0
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2025-01-28T15:39:06.688Z
Reserved: 2025-01-20T15:18:26.988Z
Link: CVE-2025-24356

Updated: 2025-01-28T15:39:02.673Z

Status : Received
Published: 2025-01-27T18:15:41.347
Modified: 2025-01-27T18:15:41.347
Link: CVE-2025-24356

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