Summary

The vulnerability allows an attacker to have infinite encryptions.

This can lead to naive attempts at brute forcing, as well as more refined attacks with the goal to learn the server secrets.

PoC js import crypto from "node:crypto";

const key = crypto.randomBytes(32); const iv = crypto.randomBytes(16); const cipher = crypto.createCipheriv("aes-256-cbc", key, iv); cipher.final()

console.log(cipher);

Expected Output js Cipheriv { decoder: null, options: undefined, Symbol(kHandle): CipherBase {} }

Actual Output js Cipheriv { events: { close: undefined, error: undefined, prefinish: [Function: prefinish], finish: undefined, drain: undefined, data: undefined, end: undefined, readable: undefined }, readableState: ReadableState { highWaterMark: 65536, buffer: [], bufferIndex: 0, length: 0, pipes: [], awaitDrainWriters: null, [Symbol(kState)]: 1048844 }, writableState: WritableState { highWaterMark: 65536, length: 0, corked: 0, onwrite: [Function: bound onwrite], writelen: 0, bufferedIndex: 0, pendingcb: 0, [Symbol(kState)]: 17580812, [Symbol(kBufferedValue)]: null }, allowHalfOpen: true, final: [Function: final], maxListeners: undefined, transform: [Function: transform], eventsCount: 1, [Symbol(kCapture)]: false, [Symbol(kCallback)]: null }

Mitigations

All users should upgrade to Deno v2.6.0 or newer.