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Weakness (CWE)

CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization

Class Draft

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

How to prevent it (8 mitigations)

  1. Architecture and Design

    In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.

  2. Architecture and Design

    Use thread-safe capabilities such as the data access abstraction in Spring.

  3. Architecture and Design

    Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.

    Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

  4. Implementation

    When using multithreading and operating on shared variables, only use thread-safe functions.

  5. Implementation

    Use atomic operations on shared variables. Be wary of innocent-looking constructs such as "x++". This may appear atomic at the code layer, but it is actually non-atomic at the instruction layer, since it involves a read, followed by a computation, followed by a write.

  6. Implementation

    Use a mutex if available, but be sure to avoid related weaknesses such as CWE-412.

  7. Implementation

    Avoid double-checked locking (CWE-609) and other implementation errors that arise when trying to avoid the overhead of synchronization.

  8. Implementation

    Disable interrupts or signals over critical parts of the code, but also make sure that the code does not go into a large or infinite loop.

Source: MITRE CWE-362

All Critical High Medium Low Exploited only Public exploit

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