CVE-2026-67213: nanoid Custom Generators Can Loop Indefinitely Vulnerability

HIGH
Advisory Identifier: GHSA-2v37-7h3g-55p8
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CVSS 5.9
CWE-835
Published
Advisory Summary

CVE-2026-67213 is a HIGH (CVSS 5.9) custom generators can loop indefinitely vulnerability (CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop')) affecting nanoid libraries in the npm ecosystem. The issue involves custom generators can loop indefinitely when size is zero. Remediation is available by upgrading affected packages to version 3.3.18, 5.1.6.

CVE-2026-67213 at a Glance

CVE Identifier CVE-2026-67213
GHSA Identifier GHSA-2v37-7h3g-55p8
Severity HIGH
CVSS v3.1 Base Score 5.9
CWE Classification CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop')
Affected Product nanoid
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 5.9

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2026-67213

To remediate this vulnerability, upgrade all affected nanoid dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

nanoid fixed: 3.3.18 
npm install nanoid@3.3.18
nanoid fixed: 5.1.6 
npm install nanoid@5.1.6
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls nanoid

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-67213, inspect your project dependencies using npm:

npm ls nanoid

Analyze the terminal output to locate any version of nanoid in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.3.18), your application is affected.

Note: The npm ls nanoid command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop'), where the product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop. In nanoid, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

nanoid (Nano ID) before 5.1.6 contains an infinite loop in the customAlphabet and customRandom functions. When these functions are configured with a size of 0, the internal generation loop never satisfies its exit condition and spins indefinitely, hanging the calling thread. An application that passes an unvalidated, attacker-controlled size of 0 to these functions is exposed to a denial-of-service condition.

CVE-2026-67213 Affected nanoid Versions

2 component(s)
Fixed Versions:
3.3.185.1.6
Product / Package Ecosystem Affected Versions Fixed Version
nanoid
npm/nanoid
npm
< 3.3.18
3.3.18
nanoid
npm/nanoid
npm
≥ 4.0.0
< 5.1.6
5.1.6

References

NVD — CVE-2026-67213 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-67213
Security Fix Commit FIX COMMIT
https://github.com/ai/nanoid/commit/cb3626d0f3342fdf179cd425fd9c4fbb92c7d0e7
Security Fix Commit FIX COMMIT
https://github.com/ai/nanoid/commit/e10f8d40ce9d1ab47f66d65a16b48086432730d0
Security Fix Commit FIX COMMIT
https://github.com/ai/nanoid/commit/f9d13f150847d117877adee3460a46eceb0cf49b
nanoid Source Repository REPOSITORY
https://github.com/ai/nanoid
nanoid Release RELEASE
https://github.com/ai/nanoid/releases/tag/3.3.17
nanoid Release RELEASE
https://github.com/ai/nanoid/releases/tag/3.3.18
nanoid Release RELEASE
https://github.com/ai/nanoid/releases/tag/5.1.6
www.vulncheck.com/advisories/nanoid-b... WEB
https://www.vulncheck.com/advisories/nanoid-before-infinite-loop-via-zero-size-in-customalphabet-and-customrandom

Frequently Asked Questions

What is CVE-2026-67213?
CVE-2026-67213 is a security vulnerability in nanoid involving custom generators can loop indefinitely when size is zero under CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop').
Which nanoid versions are affected?
Affected versions include releases prior to 3.3.18, 5.1.6 across affected packages: nanoid.
What version fixes CVE-2026-67213?
Upgrading to 3.3.18, 5.1.6 (or the latest patched release for your respective branch) resolves the vulnerability.
Is nanoid affected?
Yes, nanoid is affected in releases prior to 3.3.18, 5.1.6. Upgrade your dependency to 3.3.18, 5.1.6 or later.
What is the CVSS score of CVE-2026-67213?
CVE-2026-67213 has a CVSS v3.1 base score of 5.9 (HIGH) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2026-67213?
CVE-2026-67213 is classified under CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop') (The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.).
How can I check npm dependencies for CVE-2026-67213?
Run the dependency tree command: 'npm ls nanoid'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-2v37-7h3g-55p8",
  "modified" : "2026-08-13T15:43:00Z",
  "published" : "2026-07-29T15:31:12Z",
  "aliases" : [ "CVE-2026-67213" ],
  "summary" : "nanoid: custom generators can loop indefinitely when size is zero",
  "details" : "nanoid (Nano ID) before 5.1.6 contains an infinite loop in the customAlphabet and customRandom functions. When these functions are configured with a size of 0, the internal generation loop never satisfies its exit condition and spins indefinitely, hanging the calling thread. An application that passes an unvalidated, attacker-controlled size of 0 to these functions is exposed to a denial-of-service condition.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "nanoid"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.3.18"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "nanoid"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0"
      }, {
        "fixed" : "5.1.6"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-67213"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ai/nanoid/commit/cb3626d0f3342fdf179cd425fd9c4fbb92c7d0e7"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ai/nanoid/commit/e10f8d40ce9d1ab47f66d65a16b48086432730d0"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ai/nanoid/commit/f9d13f150847d117877adee3460a46eceb0cf49b"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/ai/nanoid"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ai/nanoid/releases/tag/3.3.17"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ai/nanoid/releases/tag/3.3.18"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ai/nanoid/releases/tag/5.1.6"
  }, {
    "type" : "WEB",
    "url" : "https://www.vulncheck.com/advisories/nanoid-before-infinite-loop-via-zero-size-in-customalphabet-and-customrandom"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-835" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-07T20:50:34Z",
    "nvd_published_at" : "2026-07-29T14:16:34Z"
  }
}