CVE-2025-24356
UDP traffic amplification via fastd's fast reconnect feature
- State
- Published
- Severity
- 6.9 Medium
- Published
- Jan 27, 2025
- Updated
- Jan 28, 2025
- Reserved
- Jan 20, 2025
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 6.9 Medium | 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 | GitHub_M |
Weaknesses
- CWE-405 Asymmetric Resource Consumption (Amplification)
Affected Products
| Product | Versions |
|---|---|
fastdneocturne |
|
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
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