CVE-2021-4239: Noiseprotocol Noise

High severity, CVSS 7.5. EPSS: 0.4% chance of exploitation in the next 30 days.

The Noise protocol implementation suffers from weakened cryptographic security after encrypting 2^64 messages, and a potential denial of service attack. After 2^64 (~18.4 quintillion) messages are encrypted with the Encrypt function, the nonce counter will wrap around, causing multiple messages to be encrypted with the same key and nonce. In a separate issue, the Decrypt function increments the nonce state even when it fails to decrypt a message. If an attacker can provide an invalid input to the Decrypt function, this will cause the nonce state to desynchronize between the peers, resulting in a failure to encrypt all subsequent messages.

Affected products

• Noiseprotocol Noise: affected versions not specified

Published 2022-12-27. Last modified 2026-06-17.