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Weakness (CWE)

CWE-502: Deserialization of Untrusted Data

Base Draft

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

How to prevent it (7 mitigations)

  1. Architecture and Design, Implementation

    If available, use the signing/sealing features of the programming language to assure that deserialized data has not been tainted. For example, a hash-based message authentication code (HMAC) could be used to ensure that data has not been modified.

  2. Implementation

    When deserializing data, populate a new object rather than just deserializing. The result is that the data flows through safe input validation and that the functions are safe.

  3. Implementation

    Explicitly define a final object() to prevent deserialization.

  4. Architecture and Design, Implementation

    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.

  5. Implementation

    Avoid having unnecessary types or gadgets (a sequence of instances and method invocations that can self-execute during the deserialization process, often found in libraries) available that can be leveraged for malicious ends. This limits the potential for unintended or unauthorized types and gadgets to be leveraged by the attacker. Add only acceptable classes to an allowlist. Note: new gadgets are constantly being discovered, so this alone is not a sufficient mitigation.

  6. Architecture and Design, Implementation

    Employ cryptography of the data or code for protection. However, it's important to note that it would still be client-side security. This is risky because if the client is compromised then the security implemented on the client (the cryptography) can be bypassed.

  7. Operation

    Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth [REF-1481].

Source: MITRE CWE-502

All Critical High Medium Low Exploited only Public exploit

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