---
title: "CVE-2026-117601: Electrum: Malicious server can replace a just-broadcast tx and try to trick user into RBF-ing it"
url: https://erroneo.us/security/cve/CVE-2026-117601/
description: "CVE-2026-117601 (electrum (PyPI)): Electrum before 4.8.3 fails to verify signatures of wallet-owned inputs in unconfirmed mempool transactions, allowing…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-10-27
date_modified: 2026-10-28
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-117601"
kev: false
cvss: 9.3
epss: 0.00176
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-117601: Electrum: Malicious server can replace a just-broadcast tx and try to trick user into RBF-ing it

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.2% , percentile 7: FIRST’s model estimates a 0.2% chance of exploitation activity in the next 30 days, higher than 7% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes electrum (PyPI) < 4.8.3, fixed in 4.8.3 . Check your lockfile, including transitive dependencies.

## What it is

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

- PyPI `electrum` < 4.8.3 → fixed: 4.8.3

## Affected products (CVE record)

- spesmilo electrum: < 4.8.3

## Severity

- VulnCheck CVSS 4.0: 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: 7.5 `CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H`
- GitHub CVSS 4.0: 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`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-11-05): 0.18% probability of exploitation activity in the next 30 days; percentile 7.

## Sources

- [GitHub Security Advisory (GHSA-6jp4-8v48-cc5v)](https://github.com/spesmilo/electrum/security/advisories/GHSA-6jp4-8v48-cc5v)
- [Patch Commit](https://github.com/spesmilo/electrum/commit/90fe30822561e515a9d2d6e5a352cc07780999eb)
- [GitHub Advisory GHSA-6jp4-8v48-cc5v](https://github.com/advisories/GHSA-6jp4-8v48-cc5v)
- [CVE.org record CVE-2026-117601](https://www.cve.org/CVERecord?id=CVE-2026-117601)
- [NVD entry CVE-2026-117601](https://nvd.nist.gov/vuln/detail/CVE-2026-117601)
- [VulnCheck Advisory: Electrum before 4.8.3 Missing Signature Verification of Mempool Transactions](https://www.vulncheck.com/advisories/electrum-before-4.8.3-missing-signature-verification-of-mempool-transactions)
- [binance.com](https://www.binance.com/en/square/post/381361716824742)

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Source page: https://erroneo.us/security/cve/CVE-2026-117601/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt