VulnerabilityModified

CVE-2021-31876

MEDIUM 6.5EPSS 1.61%

Does this matter?

Lower severity and a low EPSS score (1.61%). Track it; it rarely justifies an emergency change on its own.

Description

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.

CVSS 3.1: 6.5 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
EPSS: 1.61% probability · 75th percentile
CISA KEV: Not listed
Weakness: CWE-863
Affected: bitcoin/bitcoin
Source: cve@mitre.org

References

https://bitcoinops.org/en/newsletters/2021/05/12/Vendor Advisory
https://bitcoinops.org/en/topics/replace-by-fee/Vendor Advisory
https://en.bitcoin.it/wiki/Common_Vulnerabilities_and_Exposures#CVE-2021-31876Third Party Advisory
https://github.com/bitcoin/bitcoinThird Party Advisory
https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-May/018893.htmlMailing List, Third Party Advisory
https://bitcoinops.org/en/newsletters/2021/05/12/Vendor Advisory
https://bitcoinops.org/en/topics/replace-by-fee/Vendor Advisory
https://en.bitcoin.it/wiki/Common_Vulnerabilities_and_Exposures#CVE-2021-31876Third Party Advisory
https://github.com/bitcoin/bitcoinThird Party Advisory
https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-May/018893.htmlMailing List, Third Party Advisory

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.