Vulnerability-Lookup

CVE-2026-30827 (GCVE-0-2026-30827)

Vulnerability from cvelistv5 – Published: 2026-03-07 05:19 – Updated: 2026-03-09 20:44

Title

express-rate-limit: IPv4-mapped IPv6 addresses bypass per-client rate limiting (all IPv4 clients share one bucket on dual-stack servers)

Summary

express-rate-limit is a basic rate-limiting middleware for Express. In versions starting from 8.0.0 and prior to versions 8.0.2, 8.1.1, 8.2.2, and 8.3.0, the default keyGenerator in express-rate-limit applies IPv6 subnet masking (/56 by default) to all addresses that net.isIPv6() returns true for. This includes IPv4-mapped IPv6 addresses (::ffff:x.x.x.x), which Node.js returns as request.ip on dual-stack servers. Because the first 80 bits of all IPv4-mapped addresses are zero, a /56 (or any /32 to /80) subnet mask produces the same network key (::/56) for every IPv4 client. This collapses all IPv4 traffic into a single rate-limit bucket: one client exhausting the limit causes HTTP 429 for all other IPv4 clients. This issue has been patched in versions 8.0.2, 8.1.1, 8.2.2, and 8.3.0.

Severity ?

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE

CWE-770 - Allocation of Resources Without Limits or Throttling

Assigner

GitHub_M

References

URL

Tags

	https://github.com/express-rate-limit/express-rat…	x_refsource_CONFIRM
	https://github.com/express-rate-limit/express-rat…	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	express-rate-limit	express-rate-limit	Affected: >= 8.0.0, < 8.0.2 Affected: >= 8.1.0, < 8.1.1 Affected: >= 8.2.0, < 8.2.2

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JSON

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GHSA-46WH-PXPV-Q5GQ

Vulnerability from github – Published: 2026-03-06 18:36 – Updated: 2026-03-09 15:58

Summary

express-rate-limit: IPv4-mapped IPv6 addresses bypass per-client rate limiting on servers with dual-stack network

Details

Summary

The default keyGenerator in express-rate-limit applies IPv6 subnet masking (/56 by default) to all addresses that net.isIPv6() returns true for. This includes IPv4-mapped IPv6 addresses (::ffff:x.x.x.x), which Node.js returns as request.ip on dual-stack servers.

Because the first 80 bits of all IPv4-mapped addresses are zero, a /56 (or any /32 to /80) subnet mask produces the same network key (::/56) for every IPv4 client. This collapses all IPv4 traffic into a single rate-limit bucket: one client exhausting the limit causes HTTP 429 for all other IPv4 clients.

Details

Root Cause

In source/ip-key-generator.ts:

export function ipKeyGenerator(ip: string, ipv6Subnet: number | false = 56) {
  if (ipv6Subnet && isIPv6(ip)) {
    return `${new Address6(`${ip}/${ipv6Subnet}`).startAddress().correctForm()}/${ipv6Subnet}`
  }
  return ip
}

net.isIPv6('::ffff:192.168.1.1') returns true, so IPv4-mapped addresses enter the subnet masking path. With a /56 prefix, the start address for any ::ffff:x.x.x.x is ::, producing the key ::/56.

Proof of Concept

const { isIPv6 } = require('net');
const { Address6 } = require('ip-address');

function ipKeyGenerator(ip, ipv6Subnet = 56) {
  if (ipv6Subnet && isIPv6(ip)) {
    return `${new Address6(`${ip}/${ipv6Subnet}`).startAddress().correctForm()}/${ipv6Subnet}`;
  }
  return ip;
}

console.log(ipKeyGenerator('::ffff:192.168.1.1', 56)); // ::/56
console.log(ipKeyGenerator('::ffff:10.0.0.1', 56));    // ::/56
console.log(ipKeyGenerator('::ffff:8.8.8.8', 56));     // ::/56
// ALL produce '::/56' — same bucket

End-to-End Validation

On a dual-stack Express server (app.listen(port, '::')), tested with Express 5.2.1: - request.ip for IPv4 clients is ::ffff:127.0.0.1 - Rate limit key resolves to ::/56 - After limit requests from any IPv4 client, all other IPv4 clients receive 429

When This Occurs

Node.js dual-stack servers (default on Linux when listening on ::)
Any environment where request.ip contains IPv4-mapped IPv6 addresses
Only affects the default keyGenerator (custom key generators are not affected)

Impact

Denial of Service: A single client can block all IPv4 traffic by exhausting the shared rate limit
Affects default configuration: No special options needed to trigger this

Affected Versions

All versions of express-rate-limit between v8.0.0 and v8.2.1.

Fix

This issue was fixed in commit 14e53888cdfd1b9798faf5b634c4206409e27fc4. This fix has been included in release v8.3.0, and backported to all affected minor versions in the form of releases v8.2.2, v8.1.1, and v8.0.2.

Severity ?

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "express-rate-limit"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "8.2.0"
            },
            {
              "fixed": "8.2.2"
            }
          ],
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        }
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    },
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        "ecosystem": "npm",
        "name": "express-rate-limit"
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      "versions": [
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          "type": "ECOSYSTEM"
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  "aliases": [
    "CVE-2026-30827"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-06T18:36:56Z",
    "nvd_published_at": "2026-03-07T06:16:10Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\nThe default `keyGenerator` in express-rate-limit applies IPv6 subnet masking (`/56` by default) to all addresses that `net.isIPv6()` returns true for. This includes IPv4-mapped IPv6 addresses (`::ffff:x.x.x.x`), which Node.js returns as `request.ip` on dual-stack servers.\n\nBecause the first 80 bits of all IPv4-mapped addresses are zero, a `/56` (or any `/32` to `/80`) subnet mask produces the same network key (`::/56`) for **every** IPv4 client. This collapses all IPv4 traffic into a single rate-limit bucket: one client exhausting the limit causes HTTP 429 for all other IPv4 clients.\n\n## Details\n\n### Root Cause\n\nIn `source/ip-key-generator.ts`:\n\n```typescript\nexport function ipKeyGenerator(ip: string, ipv6Subnet: number | false = 56) {\n  if (ipv6Subnet \u0026\u0026 isIPv6(ip)) {\n    return `${new Address6(`${ip}/${ipv6Subnet}`).startAddress().correctForm()}/${ipv6Subnet}`\n  }\n  return ip\n}\n```\n\n`net.isIPv6(\u0027::ffff:192.168.1.1\u0027)` returns `true`, so IPv4-mapped addresses enter the subnet masking path. With a `/56` prefix, the start address for any `::ffff:x.x.x.x` is `::`, producing the key `::/56`.\n\n### Proof of Concept\n\n```javascript\nconst { isIPv6 } = require(\u0027net\u0027);\nconst { Address6 } = require(\u0027ip-address\u0027);\n\nfunction ipKeyGenerator(ip, ipv6Subnet = 56) {\n  if (ipv6Subnet \u0026\u0026 isIPv6(ip)) {\n    return `${new Address6(`${ip}/${ipv6Subnet}`).startAddress().correctForm()}/${ipv6Subnet}`;\n  }\n  return ip;\n}\n\nconsole.log(ipKeyGenerator(\u0027::ffff:192.168.1.1\u0027, 56)); // ::/56\nconsole.log(ipKeyGenerator(\u0027::ffff:10.0.0.1\u0027, 56));    // ::/56\nconsole.log(ipKeyGenerator(\u0027::ffff:8.8.8.8\u0027, 56));     // ::/56\n// ALL produce \u0027::/56\u0027 \u2014 same bucket\n```\n\n### End-to-End Validation\n\nOn a dual-stack Express server (`app.listen(port, \u0027::\u0027)`), tested with Express 5.2.1:\n- `request.ip` for IPv4 clients is `::ffff:127.0.0.1`\n- Rate limit key resolves to `::/56`\n- After `limit` requests from any IPv4 client, all other IPv4 clients receive 429\n\n### When This Occurs\n\n- Node.js dual-stack servers (default on Linux when listening on `::`)\n- Any environment where `request.ip` contains IPv4-mapped IPv6 addresses\n- Only affects the default `keyGenerator` (custom key generators are not affected)\n\n## Impact\n\n- **Denial of Service**: A single client can block all IPv4 traffic by exhausting the shared rate limit\n- **Affects default configuration**: No special options needed to trigger this\n\n## Affected Versions\n\nAll versions of express-rate-limit between v8.0.0 and v8.2.1.\n\n## Fix\n\nThis issue was fixed in commit 14e53888cdfd1b9798faf5b634c4206409e27fc4. This fix has been included in release v8.3.0, and backported to all affected minor versions in the form of releases v8.2.2, v8.1.1, and v8.0.2.",
  "id": "GHSA-46wh-pxpv-q5gq",
  "modified": "2026-03-09T15:58:09Z",
  "published": "2026-03-06T18:36:56Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/express-rate-limit/express-rate-limit/security/advisories/GHSA-46wh-pxpv-q5gq"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-30827"
    },
    {
      "type": "WEB",
      "url": "https://github.com/express-rate-limit/express-rate-limit/commit/14e53888cdfd1b9798faf5b634c4206409e27fc4"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/express-rate-limit/express-rate-limit"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "express-rate-limit: IPv4-mapped IPv6 addresses bypass per-client rate limiting on servers with dual-stack network"
}

FKIE_CVE-2026-30827

Vulnerability from fkie_nvd - Published: 2026-03-07 06:16 - Updated: 2026-03-11 19:00

Severity ?

7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/express-rate-limit/express-rate-limit/commit/14e53888cdfd1b9798faf5b634c4206409e27fc4	Patch
	security-advisories@github.com	https://github.com/express-rate-limit/express-rate-limit/security/advisories/GHSA-46wh-pxpv-q5gq	Exploit, Patch, Vendor Advisory

Impacted products

Vendor	Product	Version
express-rate-limit_project	express-rate-limit	*
express-rate-limit_project	express-rate-limit	*
express-rate-limit_project	express-rate-limit	8.1.0

JSON

To clipboard

{
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:express-rate-limit_project:express-rate-limit:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "AE5ED6AB-D445-4E61-86B1-FBC0659382A0",
              "versionEndExcluding": "8.0.2",
              "versionStartIncluding": "8.0.0",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:a:express-rate-limit_project:express-rate-limit:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "F501D9EB-DFE4-496D-8471-61DE755B9E05",
              "versionEndExcluding": "8.2.2",
              "versionStartIncluding": "8.2.0",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:a:express-rate-limit_project:express-rate-limit:8.1.0:*:*:*:*:*:*:*",
              "matchCriteriaId": "C56713D6-533F-424A-B511-5E63014709D8",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "express-rate-limit is a basic rate-limiting middleware for Express. In versions starting from 8.0.0 and prior to versions 8.0.2, 8.1.1, 8.2.2, and 8.3.0, the default keyGenerator in express-rate-limit applies IPv6 subnet masking (/56 by default) to all addresses that net.isIPv6() returns true for. This includes IPv4-mapped IPv6 addresses (::ffff:x.x.x.x), which Node.js returns as request.ip on dual-stack servers. Because the first 80 bits of all IPv4-mapped addresses are zero, a /56 (or any /32 to /80) subnet mask produces the same network key (::/56) for every IPv4 client. This collapses all IPv4 traffic into a single rate-limit bucket: one client exhausting the limit causes HTTP 429 for all other IPv4 clients. This issue has been patched in versions 8.0.2, 8.1.1, 8.2.2, and 8.3.0."
    },
    {
      "lang": "es",
      "value": "express-rate-limit es un middleware b\u00e1sico de limitaci\u00f3n de tasa para Express. En versiones a partir de la 8.0.0 y anteriores a las versiones 8.0.2, 8.1.1, 8.2.2 y 8.3.0, el keyGenerator predeterminado en express-rate-limit aplica enmascaramiento de subred IPv6 (/56 por defecto) a todas las direcciones para las que net.isIPv6() devuelve verdadero. Esto incluye direcciones IPv6 mapeadas a IPv4 (::ffff:x.x.x.x), que Node.js devuelve como request.ip en servidores de doble pila. Debido a que los primeros 80 bits de todas las direcciones mapeadas a IPv4 son cero, una m\u00e1scara de subred /56 (o cualquier /32 a /80) produce la misma clave de red (::/56) para cada cliente IPv4. Esto colapsa todo el tr\u00e1fico IPv4 en un \u00fanico cubo de limitaci\u00f3n de tasa: un cliente que agota el l\u00edmite causa HTTP 429 para todos los dem\u00e1s clientes IPv4. Este problema ha sido parcheado en las versiones 8.0.2, 8.1.1, 8.2.2 y 8.3.0."
    }
  ],
  "id": "CVE-2026-30827",
  "lastModified": "2026-03-11T19:00:50.690",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-03-07T06:16:10.507",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/express-rate-limit/express-rate-limit/commit/14e53888cdfd1b9798faf5b634c4206409e27fc4"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Exploit",
        "Patch",
        "Vendor Advisory"
      ],
      "url": "https://github.com/express-rate-limit/express-rate-limit/security/advisories/GHSA-46wh-pxpv-q5gq"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-770"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2026-30827 (GCVE-0-2026-30827)

GHSA-46WH-PXPV-Q5GQ

Summary

Details

Root Cause

Proof of Concept

End-to-End Validation

When This Occurs

Impact

Affected Versions

Fix

FKIE_CVE-2026-30827

Tags

Sightings

Nomenclature