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GHSA-hc33-32vw-rpp9
No affected components available
Impact
A malicious attacker can achieve Remote Code Execution (RCE) via a maliciously crafted Java deserialization gadget chain leveraged against the Ratpack session store.
If your application does not use Ratpack's session mechanism, it is not vulnerable.
Details
Attackers with the ability to write to session data, can potentially craft payloads that deserialize unsafe objects, leading to the ability to remotely execute arbitrary code. This is known as an “insecure deserialization” vulnerability, or “gadget vulnerability”.
Ratpack allows session data to be stored server side in an external system such as a relational database, or client side via user cookies. When using server side storage, the attacker would need to obtain the ability to write to the session data store. When using client side storage, the attacker would need to obtain the secrets used to encrypt and/or sign the session data stored in user cookies.
Ratpack's session mechanism allows storing serialized objects, of arbitrary types. The type must be specified when writing the data and when reading, with data only deserialized when there is an exact type match. However, in the process of deserializing an object of a known/trusted/deserialization-safe type, it may attempt to deserialize unsafe types.
By default Ratpack uses Java's built-in serialization mechanism, though other serialization providers can be used. The exact types of payloads required to enable an exploit depend on the exact serialization mechanism used.
To mitigate this vulnerability, Ratpack now employs a “strict allow-list” when deserializing (and serializing) objects to session data. All concrete types of objects serialized must be explicitly declared as safe. Some standard well known JDK types are registered by default.
Serialization is provided by implementations of SessionSerializer.
Its existing methods have been deprecated, and replaced with a new methods that accept a SessionTypeFilter that can be used to assert whether a type is allowed when serializing and deserializing.
The default serializer implementation has been updated to use this mechanism. Any proprietary implementations should also be updated to consult the type filter before serializing or deserializing data. Warnings will be logged any time an implementation that does not implement the new methods is used.
Upon upgrading to Ratpack 1.9, users of the built-in serialization mechanism will need to change their application to declare all types currently being serialized as being safe. This can be done using the new SessionModule.allowTypes() method. Please see its documentation for details...))
Patches
Ratpack 1.9.0 introduces a strict allow-list mechanism that mitigates this vulnerability when used.
Workarounds
The simplest mitigation for users of earlier versions is to reduce the likelihood of attackers being able to write to the session data store.
Alternatively or additionally, the allow-list mechanism could be manually back ported by providing an alternative implementation of SessionSerializer that uses an allow-list.
References
- https://foxglovesecurity.com/2015/11/06/what-do-weblogic-websphere-jboss-jenkins-opennms-and-your-application-have-in-common-this-vulnerability/
- https://owasp.org/www-community/vulnerabilities/Deserialization_of_untrusted_data
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data. There is a high impact on the availability of the system.
Active exploitation in the wild has been confirmed. Immediate patching or mitigation is required.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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