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Vulnerability details: VCID-9g6t-dcaz-1kh3
Vulnerability ID VCID-9g6t-dcaz-1kh3
Aliases CVE-2021-31876
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.
Status Published
Exploitability 0.5
Weighted Severity 6.2
Risk 3.1
Affected and Fixed Packages Package Details
Weaknesses (0)
There are no known CWE.
System Score Found at
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-31876
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-31876
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-31876
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-31876
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-31876
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-31876
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-31876
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-31876
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-31876
archlinux Medium https://security.archlinux.org/AVG-1486
Reference id Reference type URL
https://api.first.org/data/v1/epss?cve=CVE-2021-31876
AVG-1486 https://security.archlinux.org/AVG-1486
No exploits are available.
Exploit Prediction Scoring System (EPSS)
Percentile 0.6533
EPSS Score 0.00487
Published At April 1, 2026, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2026-04-01T18:10:06.147639+00:00 EPSS Importer Import https://epss.cyentia.com/epss_scores-current.csv.gz 38.0.0