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How CVE-2026-70603 Works
Electron’s `shell.openPath()` API is designed to open a given file path using the operating system’s default application. Prior to the patch, this function did not reject paths containing embedded null bytes (\0). In many programming languages and file systems, a null byte terminates a string; however, Electron’s implementation did not enforce this boundary, allowing an attacker to craft a malicious path that appears valid under string-only checks but resolves to a different file when actually opened.
The vulnerability arises in applications that perform string-based validation (e.g., checking file extensions, allowed directories) on user‑supplied paths without consulting the filesystem. An attacker can supply a path like "safe.pdf\0malicious.exe". The string‑only validation sees `”safe.pdf”` and approves the request, but `shell.openPath()` interprets the entire string and may open `”malicious.exe”` because the null byte is ignored or treated as a separator.
Crucially, Node.js’ built‑in `fs` APIs (e.g., fs.existsSync(), fs.stat()) do reject paths containing null bytes, throwing an error. Therefore, applications that perform a filesystem check before calling `shell.openPath()` are not affected. Only apps that rely exclusively on string manipulation without touching the filesystem are vulnerable.
The issue impacts all Electron versions below the patched releases:
– `< 39.8.6`
- `>= 40.0.0-alpha.1` to `< 40.9.0`
- `>= 41.0.0-alpha.1` to `< 41.1.1`
- `>= 42.0.0-alpha.1` to < 42.0.0-beta.1.
The fix was backported to all supported stable branches, and the advisory was published on July 27, 2026, with updates as recent as August 5, 2026.
DailyCVE Form:
Platform: Electron
Version: <39.8.6, 40.0.0-alpha.1-40.8.x, 41.0.0-alpha.1-41.1.0, 42.0.0-alpha.1-42.0.0-beta.0
Vulnerability: Path validation bypass
Severity: Moderate
Date: 2026-08-05
Prediction: 2026-07-27
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The following bash command can be used to check if your Electron app is running a vulnerable version:
Check Electron version electron --version Or if installed locally npx electron --version
Vulnerable code pattern (string‑only validation):
// Vulnerable: only checks file extension
function isSafePath(path) {
return path.endsWith('.pdf');
}
if (isSafePath(userInput)) {
// Attacker can pass "safe.pdf\0malicious.exe"
shell.openPath(userInput);
}
Fixed code (reject null bytes):
// Safe: reject any path containing a null byte
if (userInput.includes('\0')) {
throw new Error('Invalid path');
}
// Optional: also perform a filesystem check
if (fs.existsSync(userInput) && userInput.endsWith('.pdf')) {
shell.openPath(userInput);
}
Version upgrade commands:
Upgrade to a patched version npm install [email protected] or 41.1.1, 40.9.0, 39.8.6
Exploit
An attacker can craft a path that passes string‑only validation (e.g., ending with .pdf) but contains a null byte followed by a different file (e.g., malicious.exe). When the vulnerable app calls `shell.openPath()` with this string, the operating system may open the file after the null byte, allowing the attacker to launch an unintended executable or access a restricted file, bypassing the app’s security checks.
Protection
- Upgrade to one of the fixed versions:
42.0.0-beta.1,41.1.1,40.9.0, or39.8.6. - Workaround: Reject any path containing a null byte (
\0) before callingshell.openPath(). - Best practice: Always perform a filesystem check (e.g., `fs.existsSync()` or
fs.stat()) on user‑supplied paths, as Node’s `fs` APIs already reject null‑byte paths.
Impact
- Confidentiality: An attacker may open sensitive files that the app did not intend to expose.
- Integrity: Malicious executables could be launched, potentially leading to system compromise.
- Availability: The app’s validation logic can be completely bypassed, undermining any security assumptions based on string checks.
- Affected apps: Only those that pass untrusted input to `shell.openPath()` and rely solely on string‑based validation without a filesystem check. Apps that already use `fs` APIs or do not call `shell.openPath()` with untrusted data are not impacted.
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Sources:
Reported By: github.com
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