CVE-2026-117601 PUBLISHED

Electrum before 4.8.3 Missing Signature Verification of Mempool Transactions

Assigner: VulnCheck
Reserved: 27.10.2026 Published: 27.10.2026 Updated: 27.10.2026

Electrum before 4.8.3 fails to verify signatures of wallet-owned inputs in unconfirmed mempool transactions, allowing malicious servers to replace a just-broadcast transaction with a conflicting one. Attackers can swallow the user's transaction and display an invalid zero-fee copy paying an attacker address, tricking users into RBF fee-bumping and signing it.

CVSS Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CVSS Score: 9.3

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	High	Confidentiality	None
Attack Complexity	Low	Integrity	High	Integrity	None
Attack Requirements	None	Availability	High	Availability	None
Privileges Required	None
User Interaction	None

CVSS 4.0

CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
CVSS Score: 7.5

Attack Vector	Network	Scope	Unchanged
Attack Complexity	High	Confidentiality Impact	High
Privileges Required	None	Integrity Impact	High
User Interaction	Required	Availability Impact	High

CVSS 3.1

Product Status

Vendor	spesmilo
Product	electrum
Versions	Default: unaffected affected from 0 to 4.8.3 (excl.) Version 4.8.3 is unaffected

CVE-2026-117601 PUBLISHED

Electrum before 4.8.3 Missing Signature Verification of Mempool Transactions

Metrics

Product Status

Credits

References

Problem Types