CVE-2021-31876 json
Bitcoin Core 0.12.0 through 0.21.1 does not properly implement the replacement policy specified in BIP125, which makes it easier for attack…
published 2021-05-13 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-18751
- cvss
- 6.5
- version 3.1, NVD
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 1.6%
- EPSS 1.6% chance of exploitation in 30 days, percentile 76%
- public exploits
- 0
- none known
Summary
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.
Exploit prediction
1.61% chance of exploitation in the next 30 days, higher than 76% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| NVD | 3.1 | 6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L |
| NVD | 2.0 | 6.4 | AV:N/AC:L/Au:N/C:N/I:P/A:P |
Classification
- Weakness
-
- CWE-863 Incorrect Authorization
References
-
bitcoinops.org
/en/topics/replace-by-fee/
vendor-advisory
-
bitcoinops.org
/en/newsletters/2021/05/12/
vendor-advisory
-
en.bitcoin.it
/wiki/Common_Vulnerabilities_and_Exposures#CVE-2021-31876
third-party-advisory
-
github.com
/bitcoin/bitcoin
third-party-advisory
-
lists.linuxfoundation.org
/pipermail/bitcoin-dev/2021-May/018893.html
mailing-list, third-party-advisory
Sources
- CVE List CVE-2021-31876
- NVD CVE-2021-31876
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