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<title>
  Concurrent Execution using Shared Resource with Improper Synchronization
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  <h2 style="font-size: 2.7rem">
    CWE-362:
    <span
      >Concurrent Execution using Shared Resource with Improper Synchronization
    </span>
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  There is a code sequence in the programme that can run concurrently with other
  code and that needs temporary, exclusive access to a resource that is shared,
  but there is a timing window in which the shared resource can be changed by
  another code sequence that is running concurrently. This can have security
  implications when the expected synchronization is in security-critical code,
  such as recording whether a user is authenticated or modifying important state
  information that should not be influenced by an outsider. A race condition
  occurs within concurrent environments, and is effectively a property of a code
  sequence. Depending on the context, a code sequence may be in the form of a
  function call, a small number of instructions, a series of program
  invocations, etc. A race condition violates these properties, which are
  closely related:
  <br />
  <ul>
    <li>
      Exclusivity - the code sequence is given exclusive access to the shared
      resource, i.e., no other code sequence can modify properties of the shared
      resource before the original sequence has completed execution.
    </li>
    <li>
      Atomicity - the code sequence is behaviorally atomic, i.e., no other
      thread or process can concurrently execute the same sequence of
      instructions (or a subset) against the same resource.
    </li>
  </ul>
  When a "interfering code sequence" can still access the shared resource, going
  against exclusivity, a race condition is present. Programmers could believe
  that some code sequences run too quickly to be influenced by an intervening
  code sequence; if this is incorrect, atomicity is broken. For instance,
  although though the single "x++" line may appear to be atomic at the code
  layer, it is actually non-atomic at the instruction layer since it first reads
  the value of x (original value), then computes it (x+1), and finally writes it
  (save the result to x).
  <br />
  It's possible that the intervening code sequence is "trusted" or "untrusted."
  The software has a trusted interfering code sequence that the attacker cannot
  change and can only be indirectly invoked. The attacker may directly write an
  untrusted interfering code sequence, and in most cases, this code is not part
  of the vulnerable application.
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