{"id":"UBUNTU-CVE-2025-24356","details":"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.","modified":"2025-10-24T05:18:08Z","published":"2025-01-27T18:15:00Z","upstream":["CVE-2025-24356"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2025-24356"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2025-24356"},{"type":"REPORT","url":"https://github.com/neocturne/fastd/security/advisories/GHSA-pggg-vpfv-4rcv"},{"type":"REPORT","url":"https://github.com/neocturne/fastd/commit/1f233bee76b722c0b3f9024f2c39c72e9f7e5843"},{"type":"REPORT","url":"https://github.com/neocturne/fastd/commit/3940150e801d0c91460491bec32cbcc5bbc89d5f"},{"type":"REPORT","url":"https://github.com/neocturne/fastd/commit/5f63fcfc18ae9cad023fa463b152d5e14192b5a8"},{"type":"REPORT","url":"https://github.com/neocturne/fastd/commit/9df7e516378441d2d17b89f9db5c27c8312d8f12"},{"type":"REPORT","url":"https://github.com/neocturne/fastd/commit/c1a07b3f2b9066c3713c68547da700b85d60f4f7"},{"type":"REPORT","url":"https://github.com/neocturne/fastd/commit/ce1b79b12dbfa796743b5f3a50789ade965b7023"},{"type":"REPORT","url":"https://github.com/neocturne/fastd/commit/d03a0a17347efb5293e42fde7d982781e90f14ef"}],"affected":[{"package":{"name":"fastd","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/fastd@17-4ubuntu0.1?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["17-4","17-4build1","17-4ubuntu0.1"],"ecosystem_specific":{"binaries":[{"binary_name":"fastd","binary_version":"17-4ubuntu0.1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-24356.json"}},{"package":{"name":"fastd","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/fastd@18-3ubuntu0.18.04.1?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["18-2","18-2ubuntu1","18-2ubuntu2","18-3","18-3ubuntu0.18.04.1"],"ecosystem_specific":{"binaries":[{"binary_name":"fastd","binary_version":"18-3ubuntu0.18.04.1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-24356.json"}},{"package":{"name":"fastd","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/fastd@18-3ubuntu0.1?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["18-3build1","18-3ubuntu0.1"],"ecosystem_specific":{"binaries":[{"binary_name":"fastd","binary_version":"18-3ubuntu0.1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-24356.json"}},{"package":{"name":"fastd","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/fastd@22-2build1?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["21-1","22-2","22-2build1"],"ecosystem_specific":{"binaries":[{"binary_name":"fastd","binary_version":"22-2build1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-24356.json"}},{"package":{"name":"fastd","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/fastd@22-4build2?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["22-4","22-4build1","22-4build2"],"ecosystem_specific":{"binaries":[{"binary_version":"22-4build2","binary_name":"fastd"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-24356.json"}}],"schema_version":"1.7.3","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:N/SA:L"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"type":"Ubuntu","score":"medium"}]}