CVE Vulnerabilities

CVE-2021-29508

Deserialization of Untrusted Data

Published: May 11, 2021 | Modified: May 25, 2021
CVSS 3.x
9.1
CRITICAL
Source:
NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
CVSS 2.x
6.4 MEDIUM
AV:N/AC:L/Au:N/C:N/I:P/A:P
RedHat/V2
RedHat/V3
Ubuntu

Due to how Wire handles type information in its serialization format, malicious payloads can be passed to a deserializer. e.g. using a surrogate on the sender end, an attacker can pass information about a different type for the receiving end. And by doing so allowing the serializer to create any type on the deserializing end. This is the same issue that exists for .NET BinaryFormatter https://docs.microsoft.com/en-us/visualstudio/code-quality/ca2300?view=vs-2019. This also applies to the fork of Wire.

Weakness

The product deserializes untrusted data without sufficiently verifying that the resulting data will be valid.

Affected Software

Name Vendor Start Version End Version
Wire Asynkron * *

Extended Description

It is often convenient to serialize objects for communication or to save them for later use. However, deserialized data or code can often be modified without using the provided accessor functions if it does not use cryptography to protect itself. Furthermore, any cryptography would still be client-side security – which is a dangerous security assumption. Data that is untrusted can not be trusted to be well-formed. When developers place no restrictions on “gadget chains,” or series of instances and method invocations that can self-execute during the deserialization process (i.e., before the object is returned to the caller), it is sometimes possible for attackers to leverage them to perform unauthorized actions, like generating a shell.

Potential Mitigations

  • Make fields transient to protect them from deserialization.
  • An attempt to serialize and then deserialize a class containing transient fields will result in NULLs where the transient data should be. This is an excellent way to prevent time, environment-based, or sensitive variables from being carried over and used improperly.

References