CVE-2021-42765Network attack vector

Consensus stalling via network delay

Published Oct 20, 2021 · Updated Aug 4, 2024

Denial of service in Ethereum PoS consensus through 2021-10-19 allows remote attackers to stall consensus indefinitely via network delay. The attack leverages adversarial timing of network messages so validators cannot reach the protocol conditions needed to finalize decisions. Attackers able to induce or control network delay can keep consensus from progressing; the documented consequence is an availability failure without confidentiality or integrity impact.

CVSS severity7.5
High
EPSS probability0.96%
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 Ethereum PoS consensus through 2021-10-19 allows remote attackers to stall consensus indefinitely via network delay. The attack leverages adversarial timing of network messages so validators cannot reach the protocol conditions needed to finalize decisions. Attackers able to induce or control network delay can keep consensus from progressing; the documented consequence is an availability failure without confidentiality or integrity impact.

The record

CVE
CVE-2021-42765
Published
Oct 20, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1498
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.0NISTAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NISTCVSS: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 exploitUnconfirmed

Weakness, pattern, technique

T1498Network Denial of Service

Public exploit references

No public exploit references are available in this record.

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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