{"cve":"CVE-2026-30827","nvd":{"published":"2026-03-07T06:16:10.507","modified":"2026-06-17T10:32:59.050","status":"Analyzed","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":["CWE-770"],"references":["https://github.com/express-rate-limit/express-rate-limit/commit/14e53888cdfd1b9798faf5b634c4206409e27fc4","https://github.com/express-rate-limit/express-rate-limit/security/advisories/GHSA-46wh-pxpv-q5gq"],"products":["express-rate-limit_project:express-rate-limit"],"source":"nvd","synced_at":"2026-10-19T22:25:53.701907451+00:00"},"epss":{"cve":"CVE-2026-30827","score":0.00483,"percentile":0.41645,"date":"2026-11-01"},"kev":null,"osv":[{"id":"GHSA-46wh-pxpv-q5gq","url":"https://osv.dev/vulnerability/GHSA-46wh-pxpv-q5gq","summary":"express-rate-limit: IPv4-mapped IPv6 addresses bypass per-client rate limiting on servers with dual-stack network","modified":"2026-09-10T03:50:36.934542934Z","packages":[{"ecosystem":"npm","name":"express-rate-limit","purl":"pkg:npm/express-rate-limit","ranges":[">=8.2.0 <8.2.2"],"fixed":["8.2.2"]},{"ecosystem":"npm","name":"express-rate-limit","purl":"pkg:npm/express-rate-limit","ranges":[">=8.1.0 <8.1.1"],"fixed":["8.1.1"]},{"ecosystem":"npm","name":"express-rate-limit","purl":"pkg:npm/express-rate-limit","ranges":[">=8.0.0 <8.0.2"],"fixed":["8.0.2"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}