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Plack-0.9913
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/ Plack::Builder
Security Advisories (4)
CPANSA-Plack-2015-0202 (2015-02-02)

Fixed a possible directory traversal with Plack::App::File on Win32.

CPANSA-Plack-2014-0801 (2014-08-01)

Plack::App::File would previously strip trailing slashes off provided paths. This in combination with the common pattern of serving files with Plack::Middleware::Static could allow an attacker to bypass a whitelist of generated files

CPANSA-Plack-2013-0131 (2013-01-31)

Fixed directory traversal bug in Plack::App::File on win32 environments

CVE-2026-7381 (2026-04-29)

Plack::Middleware::XSendfile versions through 1.0053 for Perl can allow client-controlled path rewriting. Plack::Middleware::XSendfile allows the variation setting (sendfile type) to be set by the client via the X-Sendfile-Type header, if it is not considered in the middleware constructor or the Plack environment. A malicious client can set the X-Sendfile-Type header to "X-Accel-Redirect" to services running behind nginx reverse proxies, and then set the X-Accel-Mapping to map the path to an arbitrary file on the server. Since 1.0053, Plack::Middleware::XSendfile is deprecated and will be removed from future releases of Plack. This is similar to CVE-2025-61780 for Rack::Sendfile, although Plack::Middleware::XSendfile has some mitigations that disallow regular expressions to be used in the mapping, and only apply the mapping for the "X-Accel-Redirect" type.

NAME

Plack::Builder - OO and DSL to enable Plack Middlewares

SYNOPSIS

# in .psgi
use Plack::Builder;

my $app = sub { ... };

builder {
    enable "Plack::Middleware::Foo";
    enable "Plack::Middleware::Bar", opt => "val";
    enable "Plack::Middleware::Baz";
    $app;
};

# use URLMap

builder {
    mount "/foo" => builder {
        enable "Plack::Middleware::Foo";
        $app;
    };

    mount "/bar" => $app2;
    mount "http://example.com/" => builder { $app3 };
};

DESCRIPTION

Plack::Builder gives you a quick domain specific language (DSL) to wrap your application with Plack::Middleware subclasses. The middleware you're trying to use should use Plack::Middleware as a base class to use this DSL, inspired by Rack::Builder.

Whenever you call add on any middleware, the middleware app is pushed to the stack inside the builder, and then reversed when it actually creates a wrapped application handler, so:

builder {
    enable "Plack::Middleware::Foo";
    enable "Plack::Middleware::Bar", opt => "val";
    $app;
};

is syntactically equal to:

$app = Plack::Middleware::Bar->wrap($app, opt => "val");
$app = Plack::Middleware::Foo->wrap($app);

In other words, you're supposed to add middleware from outer to inner.

URLMap support

Plack::Builder has a native support for Plack::App::URLMap with mount method.

use Plack::Builder;
my $app = builder {
    mount "/foo" => $app1;
    mount "/bar" => builder {
        enable "Plack::Middleware::Foo";
        $app2;
    };
};

See Plack::App::URLMap's map method to see what they mean. With builder you can't use map as a DSL, for the obvious reason :)

SEE ALSO

Plack::Middleware Plack::App::URLMap