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

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-29 · updated 2026-10-29
• Weakness: CWE-835

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.

Affected products

• nanoid_project nanoid: before 3.3.16; from 4.0.0 before 5.1.16 — fixed in 3.3.16, 5.1.16
• nanoid_project nanoid: from 4.0.0 before 5.1.16; before 3.3.16 — fixed in 5.1.16, 3.3.16

How to fix

Upgrade to a fixed version: nanoid_project nanoid 3.3.16, 5.1.16; nanoid_project nanoid 5.1.16, 3.3.16. Check the vendor advisory for mitigations.

References

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

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