Remote Denial of Service via malformed NIP‑44 v2 payload

The NIP-44 v2 decryption path in the nostr crate contains a reachable panic when processing a short or empty ciphertext. After the HMAC check passes and the ciphertext is decrypted via ChaCha20, the code reads a 2‑byte unpadded‑length prefix via buffer[0..2] without first verifying that the decrypted buffer contains at least 2 bytes. A malicious sender who holds the symmetric conversation key (e.g., a direct‑message sender) can craft a payload that produces a 0 or 1‑byte decrypted buffer, causing an index‑out‑of‑bounds panic. This can be triggered remotely through any relay that delivers the crafted event to the victim's client, resulting in a denial of service. No key material, plaintext, or memory corruption occurs.

The vulnerability is present in all versions from 0.26.0 up to 0.44.4 (inclusive) and in the alpha releases 0.45.0‑alpha.1 through 0.45.0‑alpha.4. Versions 0.44.5 and 0.45.0‑alpha.5 contain the fix.

Credit

Discovered and responsibly disclosed by Muhammed Shekho (mhd-shekho.com).