Description
nanoid is a secure, URL-friendly, unique string ID generator for JavaScript. Prior to versions 3.3.12 and 5.1.11, the nanoid(size) function in index.js and index.cjs coerces the user-influenced size parameter to a signed 32-bit integer, allowing a value of 2147483648 to become -2147483648 and corrupt the process-wide CSPRNG poolOffset in fillPool(), which causes subsequent session tokens, CSRF tokens, API keys, and unique identifiers to become the deterministic string "uuuuuuuuuuuuuuuuuuuuu" until the process restarts. This issue is fixed in versions 3.3.12 and 5.1.11.
References6
- github.com/ai/nanoid/commit/7087969281cab8ba8ae3babf1894e819068…
- github.com/ai/nanoid/commit/821dfed7b5db7f88e92f56c60eef32c8135…
- github.com/ai/nanoid/commit/b0036ed60dc9facd7f1191a50dfb3076500…
- github.com/ai/nanoid/releases/tag/3.3.12
- github.com/ai/nanoid/releases/tag/5.1.11
- github.com/ai/nanoid/security/advisories/GHSA-xwg4-73v4-xw9w
Metrics
- CVSS 3.1
-
7.4
HIGH
Score source: CNA
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N - EPSS — exploit probability
- 0% percentile: 23 · as of 12 November 2026
- CWE
- CWE-190
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.