CVE-2026-30827 | express-rate-limit: IPv4-mapped IPv6 addresses bypass per-client rate limiting (all IPv4 clients share one bucket on dual-stack servers)

Exp

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 Last update: 2026-03-11 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-30827 is rated Exploit Available (50/100): CVSS High severity, with low exploitation likelihood (EPSS 0.01%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2026-30827

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2026-30827

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-03-07 — 0.01% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-30827

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2026-30827

GitHub Security Advisory for CVE-2026-30827

GHSA-46wh-pxpv-q5gq · Severity: high · Ecosystem: npm — express-rate-limit: IPv4-mapped IPv6 addresses bypass per-client rate limiting on servers with dual-stack network

OS Trackers for CVE-2026-30827

vendor priority summary link
redhat medium — https://access.redhat.com/security/cve/CVE-2026-30827

Affected software / configurations for CVE-2026-30827

Vendor Product Version Raw CPE
express-rate-limit_project express-rate-limit >= 8.0.0, < 8.0.2 cpe:2.3:a:express-rate-limit_project:express-rate-limit:*:*:*:*:*:*:*:*
express-rate-limit_project express-rate-limit >= 8.2.0, < 8.2.2 cpe:2.3:a:express-rate-limit_project:express-rate-limit:*:*:*:*:*:*:*:*
express-rate-limit_project express-rate-limit 8.1.0 cpe:2.3:a:express-rate-limit_project:express-rate-limit:8.1.0:*:*:*:*:*:*:*

References for CVE-2026-30827

cvelogic Threat Intelligence