Update dependency nanoid to v5.1.11 [SECURITY] - #224

Details

Summary

An integer overflow in nanoid(size) permanently corrupts the process-wide CSPRNG pool, causing all subsequent ID generation to return the deterministic string "uuuuuuuuuuuuuuuuuuuuu". Any application that passes user-influenced values to the size parameter loses all randomness guarantees for session tokens, CSRF tokens, and unique identifiers until process restart.

Details

nanoid() at index.js:101 coerces the size parameter with size |= 0, which converts it to a signed 32-bit integer. When size >= 2^31 (e.g., 2147483648), this wraps to -2147483648.

The negative value is passed to fillPool() (index.js:15):

function fillPool(bytes) {
  if (!pool || pool.length < bytes) {       // false: pool exists, -2B < pool.length
    pool = Buffer.allocUnsafe(bytes * POOL_SIZE_MULTIPLIER)
    crypto.getRandomValues(pool)
    poolOffset = 0
  } else if (poolOffset + bytes > pool.length) {  // false: poolOffset + (-2B) < pool.length
    crypto.getRandomValues(pool)
    poolOffset = 0
  }
  poolOffset += bytes  // poolOffset += -2147483648 → deeply negative
}

Neither branch triggers, so the pool is never refreshed. poolOffset becomes ~-2.1 billion.

Subsequent nanoid() calls execute:

for (let i = poolOffset - size; i < poolOffset; i++) {
  id += scopedUrlAlphabet[pool[i] & 63]
}

pool[negative_index] returns undefined. undefined & 63 evaluates to 0. urlAlphabet[0] is 'u'. Every ID becomes "uuuuuuuuuuuuuuuuuuuuu".

The corruption is persistent — it affects all subsequent calls in the process until ~100 million calls eventually wrap poolOffset back to positive, or the process restarts.

PoC

import { nanoid } from 'nanoid'

// Step 1: Normal operation
console.log(nanoid())  // e.g., "V1StGXR8_Z5jdHi6B-myT"

// Step 2: Trigger overflow (e.g., from an API parameter)
try { nanoid(2147483648) } catch(e) {}

// Step 3: All subsequent IDs are deterministic
console.log(nanoid())  // "uuuuuuuuuuuuuuuuuuuuu"
console.log(nanoid())  // "uuuuuuuuuuuuuuuuuuuuu"
console.log(nanoid())  // "uuuuuuuuuuuuuuuuuuuuu"
// ... forever, process-wide

Run with: node --experimental-vm-modules poc.mjs

Attack scenario: Any API endpoint that accepts a user-controlled length/size parameter (URL shortener slug length, configurable token size, etc.) and passes it to nanoid(userInput).

Impact

Complete loss of ID unpredictability and uniqueness, process-wide, from a single request.

• All session IDs, CSRF tokens, API keys, and database identifiers generated after the attack are identical and predictable
• An attacker can predict all tokens issued to other users, enabling session hijacking and authentication bypass
• The corruption is persistent (survives across requests) and affects all consumers of nanoid in the same process
• No special privileges or preconditions required — a single unauthenticated request is sufficient
• Affects any application that passes external input to the size parameter without validation

Severity

• CVSS Score: 7.4 / 10 (High)
• Vector String: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

References

• https://github.com/ai/nanoid/security/advisories/GHSA-xwg4-73v4-xw9w
• https://nvd.nist.gov/vuln/detail/CVE-2026-73086
• https://github.com/ai/nanoid/commit/7087969281cab8ba8ae3babf1894e819068b3bb4
• https://github.com/ai/nanoid/commit/821dfed7b5db7f88e92f56c60eef32c8135077c3
• https://github.com/ai/nanoid/commit/b0036ed60dc9facd7f1191a50dfb3076500202ac
• https://github.com/ai/nanoid/releases/tag/3.3.12
• https://github.com/ai/nanoid/releases/tag/5.1.11
• https://github.com/advisories/GHSA-xwg4-73v4-xw9w

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

v5.1.11

Compare Source

• Fixed breaking Nano ID by requesting big ID.

v5.1.10

Compare Source

• Fixed breaking Nano ID by requesting big ID (by @​alanzabihi).

v5.1.9

Compare Source

• Fixed npm package size regression.

v5.1.8

Compare Source

• Made cusatomAlphabet 75% faster (by @​saripovdenis).

v5.1.7

Compare Source

• Added --version to CLI (by @​mahmoodhamdi).
• Updated nanoid.js for CDN (by @​mahmoodhamdi).
• Fixed docs (by @​mahmoodhamdi).
• Fixed customRandom types (by @​oguimbal).