CVE-2026-34773: Electron: Registry key path injection in app.setAsDefaultProtocolClient on Windows
Impact On Windows, app.setAsDefaultProtocolClient(protocol) did not validate the protocol name before writing to the registry. Apps that pass untrusted input as the protocol name may allow an attacker to write to arbitrary subkeys under HKCU\Software\Classes\, potentially hijacking existing protocol handlers.
Apps are only affected if they call app.setAsDefaultProtocolClient() with a protocol name derived from external or untrusted input. Apps that use a hardcoded protocol name are not affected.
Workarounds Validate the protocol name matches /^[a-zA-Z][a-zA-Z0-9+.-]$/ before passing it to app.setAsDefaultProtocolClient().
Fixed Versions 41.0.0 40.8.1 39.8.1 38.8.6
For more information If there are any questions or comments about this advisory, please email security@electronjs.org
Other sources
Electron is a framework for writing cross-platform desktop applications using JavaScript, HTML and CSS. Prior to versions 38.8.6, 39.8.1, 40.8.1, and 41.0.0, on Windows, app.setAsDefaultProtocolClient(protocol) did not validate the protocol name before writing to the registry. Apps that pass untrusted input as the protocol name may allow an attacker to write to arbitrary subkeys under HKCU\Software\Classes\, potentially hijacking existing protocol handlers. Apps are only affected if they call app.setAsDefaultProtocolClient() with a protocol name derived from external or untrusted input. Apps that use a hardcoded protocol name are not affected. This issue has been patched in versions 38.8.6, 39.8.1, 40.8.1, and 41.0.0.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
npm/electronto a version that resolves this vulnerability.Fixed in 41.0.0 - Upgrade
Upgrade
npm/electronto a version that resolves this vulnerability.Fixed in 40.8.1 - Upgrade
Upgrade
npm/electronto a version that resolves this vulnerability.Fixed in 39.8.1 - Upgrade
Upgrade
npm/electronto a version that resolves this vulnerability.Fixed in 38.8.6 - Upgrade
Upgrade
electronto a version that resolves this vulnerability.Fixed in 38.8.6 - Upgrade
Upgrade
electronto a version that resolves this vulnerability.Fixed in 39.8.1 - Upgrade
Upgrade
electronto a version that resolves this vulnerability.Fixed in 40.8.1 - Upgrade
Upgrade
electronto a version that resolves this vulnerability.Fixed in 41.0.0 - Configuration
Before calling `app.setAsDefaultProtocolClient(protocol)`, validate that `protocol` matches `/^[a-zA-Z][a-zA-Z0-9+.-]*$/` to prevent registry key path injection from externally or untrusted-derived input.
Electron app.setAsDefaultProtocolClient (Windows registry write) protocol name validation = Validate protocol to match `/^[a-zA-Z][a-zA-Z0-9+.-]*$/` before passing it to app.setAsDefaultProtocolClient()