Is CVE-2021-4300 actively exploited?

No active exploitation of CVE-2021-4300 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2021-4300 be exploited remotely?

Yes. CVE-2021-4300 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2021-4300?

CVE-2021-4300 has a CVSS score of 9.8 (CRITICAL).

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CRITICAL

CVE-2021-4300

CWE-284Published: January 4, 2023· Updated: Jun 17, 2026

9.8

CVSS v3.1

Official Description

A vulnerability has been found in ghostlander Halcyon and classified as critical. Affected by this vulnerability is the function CBlock::AddToBlockIndex of the file src/main.cpp of the component Block Verification. The manipulation leads to improper access controls. The attack can be launched remotely. Upgrading to version 1.1.1.0-hal is able to address this issue. The identifier of the patch is 0675b25ae9cc10b5fdc8ea3a32c642979762d45e. It is recommended to upgrade the affected component. The identifier VDB-217417 was assigned to this vulnerability.

NVD Source

Risk Analysis

The Halcyon block verification component contains an improper access control vulnerability. This critical flaw allows remote attackers to potentially manipulate block verification processes.

No public exploit is known, and the vulnerability is not in the CISA KEV. It is remotely exploitable with low complexity.

Recommended Action

Upgrade to version 1.1.1.0-hal or later to resolve the issue.

Generated by the CTIWATCH analysis pipeline from this CVE's metadata (CVSS, EPSS, KEV status, exploit intelligence). Verify against vendor advisories before acting.

Technical Analysis

CVE-2021-4300 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.