CVE-2021-21369Network attack vector

HTTP JSON-RPC interruption via event-loop password checks

Published Mar 9, 2021 · Updated Aug 3, 2024

Denial of service in Hyperledger Besu before 1.5.1 allows remote attackers to interrupt HTTP JSON-RPC request processing. The login handler validates supplied passwords on the main Vert.x event loop, so repeated incorrect-password checks block other valid requests. Exposure requires HTTP JSON-RPC username-and-password authentication and knowledge of a valid username; the documented impact is service interruption.

CVSS severity6.5
Medium
EPSS probability1.50%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Hyperledger Besu before 1.5.1 allows remote attackers to interrupt HTTP JSON-RPC request processing. The login handler validates supplied passwords on the main Vert.x event loop, so repeated incorrect-password checks block other valid requests. Exposure requires HTTP JSON-RPC username-and-password authentication and knowledge of a valid username; the documented impact is service interruption.

The record

CVE
CVE-2021-21369
Published
Mar 9, 2021
Updated
Aug 3, 2024
Vendor
Hyperledger Foundation
Product
Hyperledger Besu
Classifications
CWE-400, T1499.003
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 9, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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=< 1.5.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Hyperledger Foundation · Hyperledger Besuversion=< 1.5.1

Published CVSS scores

6.5GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.0NIST NVDAV:N/AC:L/Au:S/C:N/I:N/A:P

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.003Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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