Vulnerability · Published Oct 27, 2026 · Assigned by VulnCheck

CVE-2026-117601Electrum before 4.8.3 Missing Signature Verification of Mempool Transactions

High 7.5

In plain English

A high-severity security flaw in electrum from spesmilo. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 7% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.2%top 92.8% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	electrum	no fix listed	DEBIAN-CVE-2026-117601
Debian:13	electrum	no fix listed	DEBIAN-CVE-2026-117601
Debian:14	electrum	4.8.3+dfsg-1	DEBIAN-CVE-2026-117601
PyPI	electrum	4.8.3	GHSA-6jp4-8v48-cc5v

Affected products (as reported)

Vendor	Product	Versions
spesmilo	electrum	0 – before 4.8.3

Weakness: CWE-347 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

References

GitHub Security Advisory (GHSA-6jp4-8v48-cc5v) vendor-advisory
Patch Commit patch
VulnCheck Advisory: Electrum before 4.8.3 Missing Signature Verification of Mempool Transactions third-party-advisory