CVE-2026-117601

Electrum before 4.8.3 Missing Signature Verification of Mempool Transactions

At a glance

Severity: CRITICAL 9.3
State: PUBLISHED
Published: 2026-10-27
Updated: 2026-10-27
Assigner: VulnCheck
NVD status: Awaiting Analysis

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.

Scores

Version	Score	Vector	Scored by
CVSS 4.0	CRITICAL 9.3	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	VulnCheck
CVSS 3.1	HIGH 7.5	CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H	VulnCheck
CVSS 4.0	CRITICAL 9.3	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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X	NVD · disclosure@vulncheck.com (Secondary)
CVSS 3.1	HIGH 7.5	CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H	NVD · disclosure@vulncheck.com (Primary)

Weaknesses (CWE)

CWE-347

European references

ENISA EUVD · EUVD-2026-110850
GCVE · GCVE-0-2026-117601

Affected products

Product	Versions
spesmilo · electrum	affected 0 < 4.8.3 ; unaffected 4.8.3

References

Sources

Source	Licence
CVE List (CVEProject cvelistV5)	CVE Program Terms of Use
ENISA EUVD	ENISA — reproduction authorised, source acknowledged
NVD (NIST) via fkie-cad/nvd-json-data-feeds	Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD