google-gemini/gemini-cli · critical

Security violation: Null byte detected in path.

Error message

Security violation: Null byte detected in path.

What it means

validateWorkspacePath() rejects any input containing a null byte (\0). Null bytes can truncate path strings at the C-level syscall boundary in some environments, enabling POISON NULL BYTE attacks that bypass security checks and access unintended files.

Source

Thrown at packages/a2a-server/src/utils/path_utils.ts:29

/**
 * Validates a workspace path to prevent path traversal attacks.
 *
 * @param workspacePath The path to validate.
 * @param allowedRoot The root directory the path must be within. Defaults to CWD.
 * @returns The resolved, safe path.
 * @throws An error if the path is invalid or outside the allowed root.
 */
export async function validateWorkspacePath(
  workspacePath?: string,
  allowedRoot: string = process.cwd(),
): Promise<string> {
  const trimmedPath = workspacePath?.trim();
  if (!trimmedPath) {
    return resolveToRealPath(allowedRoot);
  }

  if (trimmedPath.includes('\0')) {
    throw new Error('Security violation: Null byte detected in path.');
  }

  try {
    const canonicalAllowedRoot = resolveToRealPath(allowedRoot);
    const resolvedWorkspacePath = path.resolve(
      canonicalAllowedRoot,
      trimmedPath,
    );
    const canonicalWorkspacePath = resolveToRealPath(resolvedWorkspacePath);

    // Check if the resolved path is within the allowed root directory
    if (
      canonicalWorkspacePath !== canonicalAllowedRoot &&
      !isSubpath(canonicalAllowedRoot, canonicalWorkspacePath)
    ) {
      throw new Error(
        `Security violation: The path "${trimmedPath}" is outside the allowed root directory.`,
      );

View on GitHub (pinned to 5024443c72)

Solutions

1. Sanitize all user-supplied path input to strip or reject control characters before calling validateWorkspacePath.
2. Validate at the API boundary that paths contain only expected filename characters.
3. Treat the error as a security alert and log the source of the malicious input.

Example fix

// before
const safePath = await validateWorkspacePath(userInput); // throws if userInput has \0

// after
if (userInput.includes('\0')) {
  throw new TypeError('Invalid characters in path');
}
const safePath = await validateWorkspacePath(userInput);

function isSafePath(input: string): boolean {
  return !input.includes('\0');
}

// Before calling validateWorkspacePath:
if (!isSafePath(userInput)) {
  throw new TypeError('Path contains illegal null byte characters.');
}
const safe = await validateWorkspacePath(userInput);

function isNullByteFree(value: string): boolean {
  return !value.includes('\0');
}

When it happens

Trigger: Calling validateWorkspacePath(path) where path includes '\0' anywhere — e.g., 'safe\0/../../etc/passwd'. This is a classic injection vector or corrupted input from untrusted sources.

Common situations: Untrusted user input passed as a workspace path without sanitization; copy-paste artifacts containing embedded control characters; test fixtures with raw null bytes; binary data mistakenly interpreted as a string path.

Related errors

• Invalid taskId: ${taskId}
• Security violation: The path "${trimmedPath}" is outside the
• Invalid path: Directory traversal not allowed.
• Invalid skill name: Path traversal detected.
• Path validation failed: ${pathError}

AI-assisted analysis of google-gemini/gemini-cli@5024443c72 (2026-08-12). Data as JSON: /api/errors/0df031a10332a64d. Report an issue: GitHub.