🛡️ RUSTSEC-2026-0227 — nostr

NIP-44 v2 decryption permits resource exhaustion

The NIP-44 decryption entry point Base64-decoded the complete attacker-controlled

payload before determining its version or enforcing any size limit. For v2 payloads,

the decoded buffer was then authenticated with HMAC even when it was much larger than

the maximum payload supported by the crate's current v2 codec.

A malicious relay or event author could deliver an oversized value to an application

that decrypts NIP-44 content. The value caused memory allocation and Base64 and HMAC

work proportional to its size before authentication failed; knowledge of the

conversation key was not required to consume those initial resources. Repeated

payloads could exhaust memory or CPU and make the receiving application unavailable.

The issue does not disclose plaintext or key material and does not bypass message

authentication.

Decryption now reads only the encoded version prefix first, derives the bound from

the largest payload the current v2 encoder can emit, and rejects oversized encoded

and decoded payloads before full allocation or HMAC processing. The limit remains in

the v2 implementation so a future codec with a different length format can define its

own bound.