Summary The function processes image URLs embedded in an HTML email body without validating or restricting URI schemes. The check "!str_starts_with($myUrl, 'http')" evaluates to true for "file://" URIs, causing "file_get_contents($basedir . urldecode($myUrl))" to read arbitrary files from the server filesystem and embed them as inline MIME attachments in outgoing email. str_starts_with('file:///etc/passwd', 'http') → false !false → true // api/src/Mail.php foreach($images[2] as $i => $url) { //$isData = false; $basedir = $data = ''; $needTempFile = true; $attachmentData = ['name' => '', 'type' => '', 'file' => '', 'tmp_name' => '']; try { // do not change urls for absolute images (thanks to corvuscorax) if (!str_starts_with($url, 'data:')) { $attachmentData['name'] = basename($url); // need to resolve all sort of url if (($directory = dirname($url)) == '.') $directory = ''; $ext = pathinfo($attachmentData['name'], PATHINFO_EXTENSION); $attachmentData['type'] = MimeMagic::ext2mime($ext); if ( strlen($directory) > 1 && !str_ends_with($directory, '/')) { $directory .= '/'; } .. ... .... // processURL2InlineImages function if ( $myUrl[0]!='/' && strlen($basedir) > 1 && !str_ends_with($basedir, '/')) { $basedir .= '/'; } if ($needTempFile && empty($attachment) && !str_starts_with($myUrl, "http")) { try { $data = file_get_contents($basedir.urldecode($myUrl)); } catch (\Throwable $e) { _egw_log_exception($e); } } } if (str_starts_with($url, 'data:')) PoC 1. Log in as any authenticated EGroupware user with mail access and open the mail compose window. 2. Switch to HTML body mode and insert: "<img src="file:///etc/passwd">". 3. The server executes file_get_contents('file:///etc/passwd'), writes the content to a temp file, and attaches it as an inline MIME part. Impact An authenticated attacker can read arbitrary files accessible by the web server process, including /etc/passwd, application configuration files containing database credentials, private TLS keys, and environment files. Remediation Enforce a strict URI scheme allowlist before calling file_get_contents(). Replace the check "!str_starts_with($myUrl, 'http')" with "if (!preg_match('#^https?://#i', $myUrl)) { continue; }" to reject "file://", "ftp://", "php://", "data://", and any other non-HTTP scheme.