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TI-2021-11867 Aliases CVE-2021-31876GHSA-cm2c-8c7c-974f

Bitcoin Core 0.12.0 through 0.21.1 does not properly implement the replacement policy…

Priority LOW 32CWE-863Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Security bypass
Confidentiality · integrity · availability
None · Low · Low
Fix status
No fix listed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-863.

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.

Why it matters now

EPSS 0.01608 76th percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
——all versions—No fix listedCNA
  • — Vendor— Affected all versions Fixed in — No fix listed CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:bitcoin:bitcoin:*:*:*:*:*:*:*:*0.12.0 – 0.21.1VulnerableBitcoin
  • cpe:2.3:a:bitcoin:bitcoin:*:*:*:*:*:*:*:* Versions 0.12.0 – 0.21.1 Vulnerable ·Bitcoin

Remediation

No fixed version listed by the sources yet.

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-31876
  2. 2026-10-03 Alias added: GHSA-cm2c-8c7c-974f

References

Advisory 5

  • TI-2021-02368 Bitcoin Core before 0.19.0 might allow remote attackers to execute arbitrary code when… CVSS 3.1CRITICAL 9.8
  • TI-2017-06679 The Bitcoin Proof-of-Work algorithm does not consider a certain attack methodology… CVSS 3.1HIGH 7.5

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences