What is CVE-2026-117601?

CVE-2026-117601 is a high-severity vulnerability in Spesmilo Electrum, classified under Improper Verification of Cryptographic Signature. CVSS score: 7.5/10. Published 2026-10-27.

How severe is CVE-2026-117601?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Spesmilo Electrum

CVE-2026-117601

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.

Published 2026-10-27 · last modified 2026-10-27.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Spesmilo Electrum

Weakness classification (CWE)

CWE-347 — Improper Verification of Cryptographic Signature

References

github.com/spesmilo/electrum/security/advisories/GHSA-6jp4-8v48-cc5v (vendor-advisory)
github.com/spesmilo/electrum/commit/90fe30822561e515a9d2d6e5a352cc07780999eb (patch)
www.vulncheck.com/advisories/electrum-before-4.8.3-missing-signature-verificati… (third-party-advisory)

Frequently asked questions

What is CVE-2026-117601?: CVE-2026-117601 is a high-severity vulnerability in Spesmilo Electrum, classified under Improper Verification of Cryptographic Signature. CVSS score: 7.5/10. Published 2026-10-27.
How severe is CVE-2026-117601?: High severity. CVSS v3 base score is 7.5 out of 10.