CVE-2026-30827Public exploitNetwork attack vector

Unauthenticated IPv4 service interruption via shared bucket

Published Mar 7, 2026 · Updated Mar 7, 2026

Improper rate-limit keying in Express Rate Limit 8.0.0, 8.0.1, 8.1.0, 8.2.0, and 8.2.1 allows remote attackers to block IPv4 clients. The default ipKeyGenerator treats IPv4-mapped IPv6 addresses as native IPv6 and masks them to the same network key because their first 80 bits are zero. On dual-stack servers that expose mapped addresses through request.ip, any unauthenticated client can exhaust the shared bucket and make other IPv4 clients receive HTTP 429 responses.

CVSS severity7.5
High
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper rate-limit keying in Express Rate Limit 8.0.0, 8.0.1, 8.1.0, 8.2.0, and 8.2.1 allows remote attackers to block IPv4 clients. The default ipKeyGenerator treats IPv4-mapped IPv6 addresses as native IPv6 and masks them to the same network key because their first 80 bits are zero. On dual-stack servers that expose mapped addresses through request.ip, any unauthenticated client can exhaust the shared bucket and make other IPv4 clients receive HTTP 429 responses.

The record

CVE
CVE-2026-30827
Published
Mar 7, 2026
Updated
Mar 7, 2026
Vendor
Express Rate Limit
Product
Express Rate Limit
Classifications
CWE-770, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 7, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 7, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 8.0.0, < 8.0.2
  2. Affected versionversion=>= 8.1.0, < 8.1.1
  3. Affected versionversion=>= 8.2.0, < 8.2.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Express Rate Limit · Express Rate Limitversion=>= 8.0.0, < 8.0.2; version=>= 8.1.0, < 8.1.1; version=>= 8.2.0, < 8.2.2

Published CVSS scores

7.5GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
T1499Endpoint Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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