High · published July 3, 2026
An issue in curl’s QUIC UDP receive function allows a malicious HTTP/3 server
to trigger a remote denial of service against a curl or libcurl client.
Because the helper function discards zero-length UDP datagrams before counting
them toward the per-call packet budget, a connected QUIC peer can continuously
stream empty datagrams to indefinitely stall the client.
| Product | Versions | Fixed in |
|---|---|---|
| haxx/curl | ≥ 8.18.0, < 8.21.0 | 8.21.0 |