GHSA-rjhh-76wf-8xmw Smarty Security stream restriction bypass through stream: resource
`smarty/smarty` version `5.8.0` can read local files through PHP stream wrappers even when Smarty Security is enabled and all streams are disabled with `Security::$streams = null`.The bypass uses Smarty's built-in `stream:` resource type. A template such as:is handled as Smarty resource type `stream`, so the security check that would normally reject the underlying `php` wrapper is not applied. `StreamPlugin` then opens the nested `php://filter/...` URI directly.For comparison, the direct resource:is blocked with `stream 'php' not allowed by security setting`.Affected package:Ecosystem: Packagist / ComposerPackage: `smarty/smarty`Confirmed affected version: `5.8.0`Confirmed source reference from Composer lock: `78d259d3b971c59a0cd719c270cc5cbb740c36a7`Current stable version on Packagist at review time: `v5.8.0`Packagist usage at review time: 41,113,855 total downloads and 840,604 monthly downloadsRelevant code paths:`Smarty\Resource\BasePlugin::load(...)``Smarty\Resource\StreamPlugin::getContent(...)``Smarty\Security::isTrustedStream(...)``BasePlugin::load()` maps the built-in resource name `stream` directly to `StreamPlugin` before the code path that checks PHP stream wrappers with `stream_get_wrappers()` and `Security::isTrustedStream($type)`. `StreamPlugin::getContent()` later calls `fopen($filepath, 'r+')` on the nested URI when the resource name contains `://`.Preconditions:An application must render templates that are not fully trusted while relying on Smarty Security to restrict local files and PHP stream wrappers. The PoC sets:Local reproduction:The PoC creates a disposable template directory and a separate outside directory. It enables Smarty Security, disables all streams, and then compares three includes:`../outside/secret.tpl` to confirm the ordinary trusted-directory boundary is enforced.`php://filter/...` to confirm direct PHP streams are blocked by `Security::$streams = null`.`stream:php://filter/...` to show the built-in `stream:` resource bypasses the same restriction and reads the outside file.Run:Observed sanitized output:The `plain_dotdot_include` line shows the directory boundary is enforced for ordinary traversal. The `direct_php_filter_include` line shows the same policy rejects `php://filter` when used directly. The `stream_php_filter_include` line shows that wrapping the same URI in Smarty's `stream:` resource bypasses that restriction and reads the outside file.Impact:A template author can bypass Smarty Security stream restrictions and read local files that are readable by the PHP process. With `php://filter`, file contents can be base64 encoded and rendered back through the template. This bypasses both the intended `Security::$streams = null` restriction and the normal trusted-template-directory check that blocks `../` traversal.Duplicate checks:OSV query for `Packagist/smarty/smarty` version `5.8.0` returned no vulnerabilities.GitHub advisory query for `ecosystem=composer` and `affects=smarty/smarty` returned historical Smarty advisories, including sandbox escapes, PHP code injection, XSS, and older path traversal issues. The listed path traversal advisories affect older versions and do not describe this current `stream:php://filter` resource-wrapper bypass in 5.8.0.GitHub issue search in `smarty-php/smarty` for `stream:php://filter` returned zero results.Public searches for `Smarty StreamPlugin php://filter` and `smarty/smarty isTrustedStream stream:` did not identify a clear public duplicate during triage.Suggested remediation:When resolving the built-in `stream:` resource, parse and validate the nested URI scheme before opening it. For example, `stream:php://filter/...` should call `Security::isTrustedStream('php')`, and `Security::$streams = null` should block the resource before `StreamPlugin::getContent()` reaches `fopen()`.It would also be safer for `StreamPlugin` to reject nested stream wrappers by default unless the underlying wrapper is explicitly allowed by the active security policy.
CVSS v4.0 score: 6.9