/ 
Dancer2-2.1.0
⭐ Starred 552 / Dancer2::Serializer::JSON
Security Advisories (1)
CVE-2026-13577 (2026-07-20)

Dancer2 versions through 2.1.0 for Perl generate insecure session ids when required CSPRNG modules are unavailable. Dancer2::Core::Role::SessionFactory::generate_id silently falls back to a built-in rand-derived session id unless both Math::Random::ISAAC::XS and Crypt::URandom are available. The fallback session id is generated from a SHA-1 hash of a call to the built-in rand function, the absolute path of the Dancer2::Core::Role::SessionFactory module, an internal counter, the process id, the module instance memory address, and a shuffled string of characters (using the List::Util::shuffle function, which also uses the built-in rand function). These are all low-entropy and easily guessed sources. The built-in rand() function is seeded with 32-bits and considered unsuitable for security applications. Predictable session ids could allow an attacker to gain access to systems.

NAME

Dancer2::Serializer::JSON - Serializer for handling JSON data

VERSION

version 2.1.0

DESCRIPTION

This is a serializer engine that allows you to turn Perl data structures into JSON output and vice-versa.

ATTRIBUTES

content_type

Returns 'application/json'

METHODS

serialize($content)

Serializes a Perl data structure into a JSON string.

deserialize($content)

Deserializes a JSON string into a Perl data structure.

FUNCTIONS

from_json($content, \%options)

This is an helper available to transform a JSON data structure to a Perl data structures.

to_json($content, \%options)

This is an helper available to transform a Perl data structure to JSON.

Calling this function will not trigger the serialization's hooks.

Configuring the JSON Serializer using set engines

The JSON serializer options can be configured via set engines. The most common settings are:

allow_nonref

Ignore non-ref scalars returned from handlers. With this set the "Hello, World!" handler returning a string will be dealt with properly.

strict_utf8

If true, invalid UTF-8 bytes in data passed to the JSON encoder will cause an error. If false (default), invalid bytes are left as-is and a warning is logged.

Note: the utf8 option is forced to true internally to ensure JSON output is UTF-8 encoded bytes.

Set engines should be called prior to setting JSON as the serializer:

set engines =>
{
    serializer =>
    {
        JSON =>
        {
           allow_nonref => 1
        },
    }
};

set serializer      => 'JSON';
set content_type    => 'application/json';

Returning non-JSON data.

Handlers can return non-JSON via send_as, which overrides the default serializer:

get '/' =>
sub
{
    send_as html =>
    q{Welcome to the root of all evil...<br>step into my office.}
};

Any other non-JSON returned format supported by 'send_as' can be used.

AUTHOR

Dancer Core Developers

COPYRIGHT AND LICENSE

This software is copyright (c) 2026 by Alexis Sukrieh.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.