CVE-2017-2295 - Deserialization of Untrusted Data

Severity

60%

Complexity

68%

Confidentiality

106%

Versions of Puppet prior to 4.10.1 will deserialize data off the wire (from the agent to the server, in this case) with a attacker-specified format. This could be used to force YAML deserialization in an unsafe manner, which would lead to remote code execution. This change constrains the format of data on the wire to PSON or safely decoded YAML.

Versions of Puppet prior to 4.10.1 will deserialize data off the wire (from the agent to the server, in this case) with a attacker-specified format. This could be used to force YAML deserialization in an unsafe manner, which would lead to remote code execution. This change constrains the format of data on the wire to PSON or safely decoded YAML.

CVSS 3.0 Base Score 8.2. CVSS Attack Vector: network. CVSS Attack Complexity: high. CVSS Vector: (CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N).

CVSS 2.0 Base Score 6. CVSS Attack Vector: network. CVSS Attack Complexity: medium. CVSS Vector: (AV:N/AC:M/Au:S/C:P/I:P/A:P).

Demo Examples

Deserialization of Untrusted Data

CWE-502

This code snippet deserializes an object from a file and uses it as a UI button:


               
}
in.close();

This code does not attempt to verify the source or contents of the file before deserializing it. An attacker may be able to replace the intended file with a file that contains arbitrary malicious code which will be executed when the button is pressed.

To mitigate this, explicitly define final readObject() to prevent deserialization. An example of this is:


               
throw new java.io.IOException("Cannot be deserialized"); }

Deserialization of Untrusted Data

CWE-502

In Python, the Pickle library handles the serialization and deserialization processes. In this example derived from [R.502.7], the code receives and parses data, and afterwards tries to authenticate a user based on validating a token.


               
}
raise AuthFail

Unfortunately, the code does not verify that the incoming data is legitimate. An attacker can construct a illegitimate, serialized object "AuthToken" that instantiates one of Python's subprocesses to execute arbitrary commands. For instance,the attacker could construct a pickle that leverages Python's subprocess module, which spawns new processes and includes a number of arguments for various uses. Since Pickle allows objects to define the process for how they should be unpickled, the attacker can direct the unpickle process to call Popen in the subprocess module and execute /bin/sh.

Overview

First reported 7 years ago

2017-07-05 15:29:00

Last updated 6 years ago

2018-05-24 13:36:00

Affected Software

Debian Linux 8.0 (Jessie)

8.0

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