Executive Summary

Plack::Middleware::Session::Cookie versions through 0.21 for Perl contains a critical security vulnerability that allows an attacker to execute arbitrary code on the server.

This happens during the deserialization of cookie data when no secret key is used to sign the cookie. The middleware uses the Perl Storable module for serialization, which can be exploited by crafting malicious binary data that triggers the DESTROY method on arbitrary classes, leading to remote code execution.

The vulnerability arises because the middleware does not enforce the use of a secret key, allowing attackers to manipulate the serialized data.

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Compliance Impact

The vulnerability in Plack::Middleware::Session::Cookie versions through 0.21 allows remote code execution due to deserialization of cookie data without integrity or authenticity verification when no secret is set.

This security flaw could lead to unauthorized access or control over the server, potentially resulting in exposure or compromise of sensitive data.

Such a compromise may impact compliance with standards and regulations like GDPR or HIPAA, which require protection of personal and sensitive data against unauthorized access and mandate secure handling of session data.

Mitigations include setting a secret key to sign cookies and upgrading to versions 0.23 or later, which enforce or warn about this requirement, thereby reducing the risk of unauthorized code execution and helping maintain compliance.

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Impact Analysis

This vulnerability can allow an attacker to execute arbitrary code on your server remotely.

Such code execution can lead to full compromise of the server, including unauthorized access to data, modification or deletion of files, and potentially using the server as a launch point for further attacks.

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Detection Guidance

This vulnerability can be detected by checking if the Plack::Middleware::Session::Cookie middleware is used without specifying a secret key. Since the vulnerability arises from deserialization of cookie data without a secret, inspecting the middleware configuration for the presence or absence of a secret is essential.

There are no specific network commands provided to detect exploitation attempts, but you can audit your Perl application configuration files or code to verify if the secret option is set when initializing Plack::Middleware::Session::Cookie.

For example, you can search your codebase for the middleware usage without a secret key by running commands like:

• grep -r 'Plack::Middleware::Session::Cookie' /path/to/your/app | grep -v 'secret'
• Review logs for suspicious deserialization errors or unexpected code execution behavior related to session cookies.

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Mitigation Strategies

To mitigate this vulnerability immediately, ensure that the Plack::Middleware::Session::Cookie middleware is configured with a secret key. This secret key must be kept confidential to prevent attackers from crafting malicious cookies.

Upgrade to version 0.22 or later, where a prominent warning is issued if the middleware is used without a secret. Ideally, upgrade to version 0.23 (trial) or later, which enforces the presence of a secret by refusing to run without it.

Consider using custom serializer/deserializer classes that do not rely on the Perl Storable module to avoid this class of vulnerabilities in the future.

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