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CVE-2026-30827

express-rate-limit · Vulnerability

CVSS 3.1 7.5 HIGHCheck source for fixed versionsKEV status unknown

Original advisory

Historical advisory recorded 23 Oct 2026 15:48:27 UTC. Read the latest advisory.

cve-program · CVE-2026-30827

Published

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.

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-30827

Published

express-rate-limit

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "express-rate-limit",
                    "product": "express-rate-limit",
                    "versions": [
                        {
                            "version": ">= 8.0.0, < 8.0.2",
                            "status": "affected"
                        },
                        {
                            "version": ">= 8.1.0, < 8.1.1",
                            "status": "affected"
                        },
                        {
                            "version": ">= 8.2.0, < 8.2.2",
                            "status": "affected"
                        }
                    ]
                }

Original source record · Cite this exact observation · Complete original publisher JSON