CVE-2021-4300Network attack vector

Uncontrolled coin-stake outputs via mixed-consensus blocks

Published Jan 4, 2023 · Updated Aug 3, 2024

Improper block verification in ghostlander Halcyon before 1.1.1.0-hal allows remote attackers to mint uncontrolled coin-stake outputs. CBlock::CheckBlock accepts proof-of-work blocks containing coin-stake transactions because it fails to reject coin stakes outside proof-of-stake blocks. An attacker able to submit a valid proof-of-work block can create coin-stake output values outside consensus controls, compromising ledger integrity.

CVSS severity9.8
Critical
EPSS probability0.66%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper block verification in ghostlander Halcyon before 1.1.1.0-hal allows remote attackers to mint uncontrolled coin-stake outputs. CBlock::CheckBlock accepts proof-of-work blocks containing coin-stake transactions because it fails to reject coin stakes outside proof-of-stake blocks. An attacker able to submit a valid proof-of-work block can create coin-stake output values outside consensus controls, compromising ledger integrity.

The record

CVE
CVE-2021-4300
Published
Jan 4, 2023
Updated
Aug 3, 2024
Vendor
ghostlander
Product
Halcyon
Classifications
T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 4, 2023CVE 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?

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  1. Affected versionversion=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ghostlander · Halcyonversion=n/a

Published CVSS scores

9.8OSVCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1190Exploit Public-Facing Application

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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