AIKIDO-2026-80985

TL;DR

The NIP-44 v2 decryption path in the nostr-sdk package reads a two-byte unpadded-length prefix from the decrypted buffer via unchecked slicing without verifying that the buffer holds at least two bytes. After a valid HMAC check and ChaCha20 decryption, a short or empty ciphertext can yield a 0- or 1-byte buffer and trigger an index-out-of-bounds panic. A sender who holds the conversation key can craft such a payload and deliver it through any relay, denying service to clients that decrypt the event. The fix enforces a minimum NIP-44 v2 payload size and replaces unchecked indexing with bounds-checked reads that return an error.