CVE-2026-117601

critical

Description

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.

References

https://www.vulncheck.com/advisories/electrum-before-4.8.3-missing-signature-verification-of-mempool-transactions

https://github.com/spesmilo/electrum/security/advisories/GHSA-6jp4-8v48-cc5v

https://github.com/spesmilo/electrum/commit/90fe30822561e515a9d2d6e5a352cc07780999eb

https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-110850

Details

Source: Mitre, NVD

Published: 2026-10-27

Updated: 2026-10-28

Risk Information

CVSS v2

Base Score: 7.6

Vector: CVSS2#AV:N/AC:H/Au:N/C:C/I:C/A:C

Severity: High

CVSS v3

Base Score: 7.5

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

Severity: High

CVSS v4

Base Score: 9.3

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

Severity: Critical

EPSS

EPSS: 0.00176