CryptoSlate
ACINQ released Eclair 0.14.6 on Oct. 27 after identifying flaws that malicious Lightning nodes could exploit by manipulating unconfirmed channel funding transactions. The update requires confirmed inputs from peers for channel splices and adds safeguards for settling channels and recovering funds. ACINQ urged operators to upgrade, warning that some issues could be exploited by malicious nodes.
Why it matters
Lightning channels can be funded or adjusted through splicing, but a peer contributing an unconfirmed input could double-spend it after a splice is signed. If the channel then closes on Bitcoin, pending payments secured by HTLCs could be exposed because settlement depends on the invalidated funding transaction. The issues describe a potential risk, not a confirmed theft, and the extent of any real-world exploitation is unknown.
Eclair 0.14.6 enables a safeguard by default that requires confirmed peer inputs and blocks further splices on top of unconfirmed funding changes. ACINQ also advised against using its optional zero-fee commitment feature when splicing with untrusted peers; the feature is disabled by default.
Market impact
The patch updates settlement logic to use funding recognized by the Bitcoin Core backend, reverting to the latest confirmed state when needed. It also improves recognition of transactions miners confirm after Eclair stops tracking them as the preferred settlement route, allowing the software to try to recover related outputs.
Operators on older versions remain exposed to the identified risks. Existing payment channels can stay open during the upgrade, which requires stopping Eclair, installing the new version and restarting the node.
Frequently asked questions
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How could unconfirmed channel funding put Lightning payments at risk?
A malicious peer could double-spend an unconfirmed input after a splice is signed. If the channel then closes on Bitcoin, pending HTLC payments could be exposed because settlement depends on the invalidated funding transaction.
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What protection does Eclair 0.14.6 enable by default?
It requires confirmed inputs from peers for channel splices and blocks additional splices on top of unconfirmed funding changes.
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How does the update change channel settlement?
Eclair selects a commitment transaction backed by funding recognized by its Bitcoin Core backend, falling back to the latest confirmed funding state when necessary.
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Does ACINQ report that attackers stole funds?
No confirmed theft is reported. ACINQ describes potential security exposure, and the extent of any real-world exploitation is unknown.
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Can operators upgrade without closing existing payment channels?
Yes. Existing channels can remain open during the upgrade, which requires stopping Eclair, installing version 0.14.6 and restarting the node.
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