Electrum is a Bitcoin wallet app. It talks to servers to learn about payments. A bad server can hide a payment you just sent and show a fake one that pays a thief instead. If you then use the 'increase fee' button, you sign the fake payment and the thief gets paid. Electrum 4.8.3 fixes this. Electrum says it is already happening.
- Status
- Patched: update now
- Being attacked?
- Yes[1]
- Severity
- High
- Updated
Electrum's advisory says some servers are doing this right now, and two users reported it. One lost money. Severity: Electrum's own advisory rates it High. First reported .
Am I affected?
You are at risk if you use Electrum older than 4.8.3 and connect to servers you do not run yourself. Electrum says people who connect to a server they trust, such as their own, are not affected.
| App | Device | Affected | Fixed in |
|---|---|---|---|
| Electrum | Windows | Electrum older than 4.8.3 | 4.8.3[1][2] |
| Electrum | Mac | Electrum older than 4.8.3 | 4.8.3[1][2] |
| Electrum | Linux | Electrum older than 4.8.3 | 4.8.3[1][2] |
How to check your version
These checks only look. They do not change anything on your computer.
Electrum on Windows
Easy way: Open Electrum. Click Help > About Electrum.
Or type this in PowerShellRead-only. It only reads the version and changes nothing.
Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\*','HKLM:\SOFTWARE\WOW6432Node\Microsoft\Windows\CurrentVersion\Uninstall\*','HKCU:\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\*' -ErrorAction SilentlyContinue | Where-Object DisplayName -like '*Electrum*' | Select-Object DisplayName,DisplayVersion
Electrum on Mac
Easy way: Open Electrum. Click Help > About Electrum.
Or type this in TerminalRead-only. It only reads the version and changes nothing.
defaults read "/Applications/Electrum.app/Contents/Info" CFBundleShortVersionString
Electrum on Linux
Easy way: Open the app and look in its Help or About menu, or check your software manager.
How to fix it
- Go to electrum.org and download Electrum 4.8.3 or newer. Check the signature the way the website explains.
- Install it over your old copy. Your wallet files stay in place.
- Until you update: before you sign ANY payment (including a fee increase), read the address and the amount on screen to make sure they are right.
- Do not use the 'increase fee' button on a payment you do not recognize.
More on each app: Is my Electrum up to date?
Official links
Check before installing, and only use these official links or the app's own update button.
For AI agents
This page as data: /incidents/electrum-wallet-fake-server-fee-bump-theft.json. All problems: /feed.json. Use read-only checks only, and ask before installing anything.
Tracking numbers (CVE): CVE-2026-117601
Sources
- GitHub advisoryElectrum security advisory GHSA-6jp4-8v48-cc5v (Oct 24, 2026)
- MakerElectrum release notes for 4.8.3 (Oct 23, 2026) (Oct 23, 2026)
"Maker", "CISA", "NVD", "GitHub advisory" and "Official notice" are official sources. "Researcher" and "News" are extra context.