{"id":"CVE-2025-24356","state":"PUBLISHED","title":"UDP traffic amplification via fastd's fast reconnect feature","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.","publishedAt":"2025-01-27T17:31:38.541Z","updatedAt":"2025-01-28T15:39:06.688Z","severity":{"score":6.9,"label":"Medium","version":"4.0","vector":"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","source":"GitHub_M"},"assigner":"GitHub_M","products":["neocturne fastd"],"affected":[{"vendor":"neocturne","product":"fastd","versions":[{"version":"< 23","status":"affected"}]}],"references":["https://github.com/neocturne/fastd/security/advisories/GHSA-pggg-vpfv-4rcv","https://github.com/neocturne/fastd/commit/1f233bee76b722c0b3f9024f2c39c72e9f7e5843","https://github.com/neocturne/fastd/commit/3940150e801d0c91460491bec32cbcc5bbc89d5f","https://github.com/neocturne/fastd/commit/5f63fcfc18ae9cad023fa463b152d5e14192b5a8","https://github.com/neocturne/fastd/commit/9df7e516378441d2d17b89f9db5c27c8312d8f12","https://github.com/neocturne/fastd/commit/c1a07b3f2b9066c3713c68547da700b85d60f4f7","https://github.com/neocturne/fastd/commit/ce1b79b12dbfa796743b5f3a50789ade965b7023","https://github.com/neocturne/fastd/commit/d03a0a17347efb5293e42fde7d982781e90f14ef"],"weaknesses":["CWE-405"],"ingestedAt":"2026-10-29T20:08:47.682Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2025/24xxx/CVE-2025-24356.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.1","cveMetadata":{"cveId":"CVE-2025-24356","state":"PUBLISHED","datePublished":"2025-01-27T17:31:38.541Z","dateUpdated":"2025-01-28T15:39:06.688Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2025-01-20T15:18:26.988Z"},"containers":{"cna":{"title":"UDP traffic amplification via fastd's fast reconnect feature","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"neocturne","product":"fastd","versions":[{"version":"< 23","status":"affected"}]}],"references":[{"url":"https://github.com/neocturne/fastd/security/advisories/GHSA-pggg-vpfv-4rcv","name":"https://github.com/neocturne/fastd/security/advisories/GHSA-pggg-vpfv-4rcv","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/neocturne/fastd/commit/1f233bee76b722c0b3f9024f2c39c72e9f7e5843","name":"https://github.com/neocturne/fastd/commit/1f233bee76b722c0b3f9024f2c39c72e9f7e5843","tags":["x_refsource_MISC"]},{"url":"https://github.com/neocturne/fastd/commit/3940150e801d0c91460491bec32cbcc5bbc89d5f","name":"https://github.com/neocturne/fastd/commit/3940150e801d0c91460491bec32cbcc5bbc89d5f","tags":["x_refsource_MISC"]},{"url":"https://github.com/neocturne/fastd/commit/5f63fcfc18ae9cad023fa463b152d5e14192b5a8","name":"https://github.com/neocturne/fastd/commit/5f63fcfc18ae9cad023fa463b152d5e14192b5a8","tags":["x_refsource_MISC"]},{"url":"https://github.com/neocturne/fastd/commit/9df7e516378441d2d17b89f9db5c27c8312d8f12","name":"https://github.com/neocturne/fastd/commit/9df7e516378441d2d17b89f9db5c27c8312d8f12","tags":["x_refsource_MISC"]},{"url":"https://github.com/neocturne/fastd/commit/c1a07b3f2b9066c3713c68547da700b85d60f4f7","name":"https://github.com/neocturne/fastd/commit/c1a07b3f2b9066c3713c68547da700b85d60f4f7","tags":["x_refsource_MISC"]},{"url":"https://github.com/neocturne/fastd/commit/ce1b79b12dbfa796743b5f3a50789ade965b7023","name":"https://github.com/neocturne/fastd/commit/ce1b79b12dbfa796743b5f3a50789ade965b7023","tags":["x_refsource_MISC"]},{"url":"https://github.com/neocturne/fastd/commit/d03a0a17347efb5293e42fde7d982781e90f14ef","name":"https://github.com/neocturne/fastd/commit/d03a0a17347efb5293e42fde7d982781e90f14ef","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"LOW","baseScore":6.9,"baseSeverity":"MEDIUM","vectorString":"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","version":"4.0"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-405","lang":"en","description":"CWE-405: Asymmetric Resource Consumption (Amplification)","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2025-01-27T17:31:38.541Z"},"source":{"advisory":"GHSA-pggg-vpfv-4rcv","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2025-01-28T15:38:54.975943Z","id":"CVE-2025-24356","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2025-01-28T15:39:06.688Z"}}]}}}