CVE-2021-31876

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    CVE-2021-31876

    Published: 13 May 2021Last Modified: 9 Jul 2026

    Summary:

    Details: Bitcoin Core 0.12.0 through 0.21.1 does not properly implement the replacement policy specified in BIP125, which makes it easier for attackers to trigger a loss of funds, or a denial of service attack against downstream projects such as Lightning network nodes. An unconfirmed child transaction with nSequence = 0xff_ff_ff_ff, spending an unconfirmed parent with nSequence <= 0xff_ff_ff_fd, should be replaceable because there is inherited signaling by the child transaction. However, the actual PreChecks implementation does not enforce this. Instead, mempool rejects the replacement attempt of the unconfirmed child transaction.

    References: https://bitcoinops.org/en/newsletters/2021/05/12/, https://bitcoinops.org/en/topics/replace-by-fee/, https://en.bitcoin.it/wiki/Common_Vulnerabilities_and_Exposures#CVE-2021-31876, https://github.com/bitcoin/bitcoin, https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-May/018893.html

    Affected packages

    Package

    Name:

    Purl:

    Affected ranges

    Type: GIT

    Events:

    Introduced- 188ca9c305d3dd0fb462b9d6a44048b1d99a05f3
    Fixed -None

    Affected versions

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High
    CVE-2021-31876 | CVE-DB