Antoine Riard

**Name of the Vulnerable Software and Affected Versions** Bitcoin Core versions prior to 27.3 **Description** The issue allows for transaction-relay jamming via an off-chain protocol attack. This can change the outcome of an HTLC (Hashed Timelock Contract) because a flood of transaction traffic prevents propagation of certain Lightning channel transactions. The vulnerability poses a threat to the Bitcoin Lightning Network, potentially disrupting transactions and leading to financial losses. **Recommendations** For Bitcoin Core versions prior to 27.3, update to version 27.3 or later to resolve the issue. As a temporary workaround, consider restricting the use of HTLCs until a patch is applied. Avoid using the `transaction-relay` feature in the affected Bitcoin Core versions until the issue is resolved.

**Name of the Vulnerable Software and Affected Versions** Samourai Wallet Stonewallx2 version 0.99.98e **Description** The issue allows a denial of service via a P2P coinjoin. The attacker and victim must follow each other's paynym. Then, the victim must try to collaborate with the attacker for a Stonewallx2 transaction. Next, the attacker broadcasts a tx, spending the inputs used in Stonewallx2 before the victim can broadcast the collaborative transaction. The attacker does not signal opt in RBF, and uses the lowest fee rate. This would result in the victim being unable to perform Stonewallx2. The attacker could use multiple paynyms. **Recommendations** As a temporary workaround, consider disabling the Stonewallx2 feature until a patch is available. Restrict access to P2P coinjoin transactions to minimize the risk of exploitation. Avoid collaborating with untrusted paynyms for Stonewallx2 transactions.

**Name of the Vulnerable Software and Affected Versions** ACINQ Eclair versions prior to 0.6.3 **Description** The issue allows for loss of funds due to dust HTLC exposure. **Recommendations** For versions prior to 0.6.3, update to version 0.6.3 or later to resolve the issue.

**Name of the Vulnerable Software and Affected Versions** Bitcoin Core versions 0.12.0 through 0.21.1 **Description** The issue is related to the incorrect replacement of a child transaction in the Bitcoin Core implementation, specifically in the PreChecks functionality. This can be exploited by a remote attacker to compromise data integrity and cause a denial of service. The vulnerability arises from the improper implementation of the replacement policy as specified in BIP125, making it easier for attackers to trigger a loss of funds or launch a denial of service attack against downstream projects, such as Lightning network nodes. The problem occurs when an unconfirmed child transaction with `nSequence` = `0xff ff ff ff`, spending an unconfirmed parent with `nSequence` <= `0xff ff ff fd`, is not properly replaced due to the lack of enforcement of inherited signaling by the child transaction in the PreChecks implementation. **Recommendations** For Bitcoin Core versions 0.12.0 through 0.21.1, consider updating to a version that properly implements the replacement policy specified in BIP125 to prevent the exploitation of this issue. As a temporary workaround, restrict the use of unconfirmed child transactions with `nSequence` = `0xff ff ff ff` to minimize the risk of exploitation. Avoid using the `nSequence` parameter in unconfirmed transactions until the issue is resolved.

**Name of the Vulnerable Software and Affected Versions** LND (Lightning Network Daemon) versions prior to 0.11.0-beta **Description** The issue concerns a problem in the invoice database where LND failed to verify the settlement of an outgoing off-chain HTLC before releasing the preimage while claiming a received HTLC output on-chain. This could lead to a hash-and-amount collision with an invoice, causing the preimage for an expected payment to be released instead. A malicious peer could intercept an HTLC, probe the preimage through a colluding relayed HTLC, and steal the intercepted HTLC, resulting in a loss of funds and weakened receiver privacy. **Recommendations** For versions prior to 0.11.0-beta, update to version 0.11.0-beta or later to resolve the issue.