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CVE-2026-30827

Express-rate-limit denial of service

7.5 HIGHPublic exploitEPSS 0.53%
  1. Published7 Mar 2026

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 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Express-rate-limit≥ 8.0.0 < 8.0.2 · ≥ 8.2.0 < 8.2.2 · 8.1.0

Remediation

Fixed in
Express-rate-limit≥ 8.0.2

References

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Frequently asked

Is CVE-2026-30827 being actively exploited?

CVE-2026-30827 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.53%.

How severe is CVE-2026-30827?

CVE-2026-30827 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.53% probability of exploitation.

Which products are affected by CVE-2026-30827?

Affected products include Express-rate-limit.

How do I fix CVE-2026-30827?

Upgrade affected software to a fixed version, for example Express-rate-limit 8.0.2 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-30827 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.