CVSS 3.1
7.5 highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HCVE-2026-30827
High (7.5) in express-rate-limit project express-rate-limit. EPSS 0.5% chance of exploitation in the next 30 days. Fixed in express-rate-limit 8.0.2, 8.1.1, 8.2.2.
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
- EPSS
- 0.5% chance of exploitation in the next 30 days; higher than 41% of CVEs (scores of 2026-10-31)
- CWE
- CWE-770
- Published
- Modified
- Record from
- the NVD, synced
Affected
- express-rate-limit_project:express-rate-limit
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-46wh-pxpv-q5gq | npm | express-rate-limit | >=8.2.0 <8.2.2 | 8.2.2 |
| GHSA-46wh-pxpv-q5gq | npm | express-rate-limit | >=8.1.0 <8.1.1 | 8.1.1 |
| GHSA-46wh-pxpv-q5gq | npm | express-rate-limit | >=8.0.0 <8.0.2 | 8.0.2 |