CWE-502Deserialization of Untrusted Data

Description

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

Common consequences

• Integrity→Modify Application Data,Unexpected State
  Attackers can modify unexpected objects or data that was assumed to be safe from modification. Deserialized data or code could be modified without using the provided accessor functions, or unexpected functions could be invoked.
• Availability→DoS: Resource Consumption (CPU)
  If a function is making an assumption on when to terminate, based on a sentry in a string, it could easily never terminate.
• Other→Varies by Context
  The consequences can vary widely, because it depends on which objects or methods are being deserialized, and how they are used. Making an assumption that the code in the deserialized object is valid is dangerous and can enable exploitation.

Potential mitigations

• 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.
• 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.
• Implementation
  Explicitly define a final object() to prevent deserialization.
• Architecture and Design,Implementation
  [object Object]
• 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
• 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.
• 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].

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