High [CVE-2026-73086] Predictable ID generation due to integer overflow

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. A flaw was found in nanoid, a JavaScript library for generating unique string IDs.

A remote attacker could exploit an integer overflow vulnerability by providing a specific input to the `nanoid(size)` function. This issue causes the internal random number generator to become predictable, leading to the generation of identical identifiers for session tokens, security tokens (Cross-Site Request Forgery (CSRF) tokens), and API keys.

Such predictability could allow an attacker to bypass security measures that rely on unique and random identifiers. The attack requires specific conditions, contributing to its Important severity rather than Critical.

Red Hat severity: Important — CVSS 7.4 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N). Weakness: CWE-1241.