CVE-2021-41591Network attack vector

Fund loss via unbounded dust HTLC exposure

Published Oct 4, 2021 · Updated Aug 4, 2024

Resource allocation flaw in ACINQ Eclair before 0.6.3 allows remote attackers to cause fund loss through dust HTLC flooding. Eclair fails to cap the aggregate value of pending HTLCs that are too small to claim on-chain, so a forced channel close trims them from the commitment transaction and transfers their value to miner fees. Exploitation requires a malicious channel peer to accumulate dust HTLCs and force-close the channel; the default 30-HTLC limit reduces but does not eliminate per-channel loss.

CVSS severity9.4
Critical
EPSS probability1.70%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource allocation flaw in ACINQ Eclair before 0.6.3 allows remote attackers to cause fund loss through dust HTLC flooding. Eclair fails to cap the aggregate value of pending HTLCs that are too small to claim on-chain, so a forced channel close trims them from the commitment transaction and transfers their value to miner fees. Exploitation requires a malicious channel peer to accumulate dust HTLCs and force-close the channel; the default 30-HTLC limit reduces but does not eliminate per-channel loss.

The record

CVE
CVE-2021-41591
Published
Oct 4, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-770
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 4, 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

9.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H
7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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

CWE-770Allocation of Resources Without Limits or Throttling

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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