Tag Archives: Unrestricted Externally Accessible Lock

CWE-412 – Unrestricted Externally Accessible Lock

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Description

The software properly checks for the existence of a lock, but the lock can be externally controlled or influenced by an actor that is outside of the intended sphere of control.

This prevents the software from acting on associated resources or performing other behaviors that are controlled by the presence of the lock. Relevant locks might include an exclusive lock or mutex, or modifying a shared resource that is treated as a lock. If the lock can be held for an indefinite period of time, then the denial of service could be permanent.

Modes of Introduction:

– Architecture and Design

 

 

Related Weaknesses

CWE-667
CWE-410

 

Consequences

Availability: DoS: Resource Consumption (Other)

When an attacker can control a lock, the program may wait indefinitely until the attacker releases the lock, causing a denial of service to other users of the program. This is especially problematic if there is a blocking operation on the lock.

 

Potential Mitigations

Phase: Architecture and Design, Implementation

Description: 

Use any access control that is offered by the functionality that is offering the lock.

Phase: Architecture and Design, Implementation

Description: 

Use unpredictable names or identifiers for the locks. This might not always be possible or feasible.

Phase: Architecture and Design

Description: 

Consider modifying your code to use non-blocking synchronization methods.

CVE References

  • CVE-2001-0682
    • Program can not execute when attacker obtains a mutex.
  • CVE-2002-1914
    • Program can not execute when attacker obtains a lock on a critical output file.
  • CVE-2002-1915
    • Program can not execute when attacker obtains a lock on a critical output file.
  • CVE-2002-0051
    • Critical file can be opened with exclusive read access by user, preventing application of security policy. Possibly related to improper permissions, large-window race condition.
  • CVE-2000-0338
    • Chain: predictable file names used for locking, allowing attacker to create the lock beforehand. Resultant from permissions and randomness.
  • CVE-2000-1198
    • Chain: Lock files with predictable names. Resultant from randomness.
  • CVE-2002-1869
    • Product does not check if it can write to a log file, allowing attackers to avoid logging by accessing the file using an exclusive lock. Overlaps unchecked error condition. This is not quite CWE-412, but close.