AIKIDO-2026-54143

TL;DR

The DTLS handshake reassembler sizes each reassembly buffer from the full-message length declared in a handshake fragment header, a 24-bit value up to about 16 MiB, without bounding it against the peer's configured maximum handshake message size. Reassemblers are created per message sequence across the receive-ahead window at epoch zero, before any signature or Finished verification. A few small datagrams carrying minimal fragments with large declared lengths therefore commit large amounts of heap per peer, causing a pre-authentication denial of service. The fix bounds the reassembly allocation by the peer's maximum handshake message size before allocating.