Description
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.
Published: 2026-03-07
Score: 7.5 High
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

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Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-46wh-pxpv-q5gq express-rate-limit: IPv4-mapped IPv6 addresses bypass per-client rate limiting on servers with dual-stack network
History

Wed, 11 Mar 2026 19:15:00 +0000

Type Values Removed Values Added
First Time appeared Express-rate-limit Project
Express-rate-limit Project express-rate-limit
CPEs cpe:2.3:a:express-rate-limit_project:express-rate-limit:*:*:*:*:*:*:*:*
cpe:2.3:a:express-rate-limit_project:express-rate-limit:8.1.0:*:*:*:*:*:*:*
Vendors & Products Express-rate-limit Project
Express-rate-limit Project express-rate-limit

Tue, 10 Mar 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-1389
References
Metrics threat_severity

None

threat_severity

Moderate


Mon, 09 Mar 2026 21:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Mon, 09 Mar 2026 10:15:00 +0000

Type Values Removed Values Added
First Time appeared Express-rate-limit
Express-rate-limit express-rate-limit
Vendors & Products Express-rate-limit
Express-rate-limit express-rate-limit

Sat, 07 Mar 2026 05:30:00 +0000

Type Values Removed Values Added
Description 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.
Title express-rate-limit: IPv4-mapped IPv6 addresses bypass per-client rate limiting (all IPv4 clients share one bucket on dual-stack servers)
Weaknesses CWE-770
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}


Subscriptions

Express-rate-limit Express-rate-limit
Express-rate-limit Project Express-rate-limit
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-03-09T20:44:25.979Z

Reserved: 2026-03-05T21:06:44.606Z

Link: CVE-2026-30827

cve-icon Vulnrichment

Updated: 2026-03-09T20:42:01.780Z

cve-icon NVD

Status : Analyzed

Published: 2026-03-07T06:16:10.507

Modified: 2026-03-11T19:00:50.690

Link: CVE-2026-30827

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-03-07T05:19:08Z

Links: CVE-2026-30827 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-03-09T10:05:53Z

Weaknesses