CAPEC-29: Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions
Description
This attack targets a race condition occurring between the time of check (state) for a resource and the time of use of a resource. A typical example is file access. The adversary can leverage a file access race condition by running the race, meaning that they would modify the resource between the first time the target program accesses the file and the time the target program uses the file. During that period of time, the adversary could replace or modify the file, causing the application to behave unexpectedly.
- Likelihood of attack
- High
- Typical severity
- High
- Abstraction
- StandardA specific methodology or technique used in an attack.
Mechanism of attack: Manipulate Timing and State
Prerequisites
- A resource is access/modified concurrently by multiple processes.
- The adversary is able to modify resource.
- A race condition exists while accessing a resource.
Skills required
- MediumThis attack can get sophisticated since the attack has to occur within a short interval of time.
Consequences
- Integrity
Modify Data
- ConfidentialityAccess ControlAuthorization
Gain Privileges
- ConfidentialityIntegrityAvailability
Alter Execution Logic
- Confidentiality
Read Data
- Availability
Resource Consumption
Denial of Service
Mitigations
- Use safe libraries to access resources such as files.
- Be aware that improper use of access function calls such as chown(), tempfile(), chmod(), etc. can cause a race condition.
- Use synchronization to control the flow of execution.
- Use static analysis tools to find race conditions.
- Pay attention to concurrency problems related to the access of resources.
Related weaknesses (CWE)
- CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
- CWE-366Race Condition within a Thread
- CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition
- CWE-368Context Switching Race Condition
- CWE-370Missing Check for Certificate Revocation after Initial Check
- CWE-662Improper Synchronization
- CWE-663Use of a Non-reentrant Function in a Concurrent Context
- CWE-665Improper Initialization
- CWE-691Insufficient Control Flow Management