CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition
CWE版本: 4.18
更新日期: 2025-09-09
弱点描述
The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.
常见后果
影响范围: Integrity Other
技术影响: Alter Execution Logic Unexpected State
说明: The attacker can gain access to otherwise unauthorized resources.
影响范围: Integrity Other
技术影响: Modify Application Data Modify Files or Directories Modify Memory Other
说明: Race conditions such as this kind may be employed to gain read or write access to resources which are not normally readable or writable by the user in question.
影响范围: Integrity Other
技术影响: Other
说明: The resource in question, or other resources (through the corrupted one), may be changed in undesirable ways by a malicious user.
影响范围: Non-Repudiation
技术影响: Hide Activities
说明: If a file or other resource is written in this method, as opposed to in a valid way, logging of the activity may not occur.
影响范围: Non-Repudiation Other
技术影响: Other
说明: In some cases it may be possible to delete files a malicious user might not otherwise have access to, such as log files.
影响范围: Other
技术影响: Unexpected State
说明: The product may perform invalid actions when the resource is in an unexpected state.
潜在缓解措施
阶段: Implementation
描述: The most basic advice for TOCTOU vulnerabilities is to not perform a check before the use. This does not resolve the underlying issue of the execution of a function on a resource whose state and identity cannot be assured, but it does help to limit the false sense of security given by the check.
阶段: Implementation
描述: When the file being altered is owned by the current user and group, set the effective gid and uid to that of the current user and group when executing this statement.
阶段: Architecture and Design
描述: Limit the interleaving of operations on files from multiple processes.
阶段: Implementation Architecture and Design
描述: If you cannot perform operations atomically and you must share access to the resource between multiple processes or threads, then try to limit the amount of time (CPU cycles) between the check and use of the resource. This will not fix the problem, but it could make it more difficult for an attack to succeed.
阶段: Implementation
描述: Recheck the resource after the use call to verify that the action was taken appropriately.
阶段: Architecture and Design
描述: Ensure that some environmental locking mechanism can be used to protect resources effectively.
阶段: Implementation
描述: Ensure that locking occurs before the check, as opposed to afterwards, such that the resource, as checked, is the same as it is when in use.
检测方法
方法: Automated Static Analysis
Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
有效性: High
观察示例
参考: CVE-2015-1743
TOCTOU in sandbox process allows installation of untrusted browser add-ons by replacing a file after it has been verified, but before it is executed
参考: CVE-2003-0813
Chain: A multi-threaded race condition (CWE-367) allows attackers to cause two threads to process the same RPC request, which causes a use-after-free (CWE-416) in one thread
参考: CVE-2004-0594
PHP flaw allows remote attackers to execute arbitrary code by aborting execution before the initialization of key data structures is complete.
参考: CVE-2008-2958
chain: time-of-check time-of-use (TOCTOU) race condition in program allows bypass of protection mechanism that was designed to prevent symlink attacks.
参考: CVE-2008-1570
chain: time-of-check time-of-use (TOCTOU) race condition in program allows bypass of protection mechanism that was designed to prevent symlink attacks.
引入模式
| 阶段 | 说明 |
|---|---|
| Implementation | This weakness can be security-relevant when an attacker can influence the state of the resource between check and use. This can happen with shared resources such as files, memory, or even variables in multithreaded programs. |
适用平台
编程语言
分类映射
| 分类名称 | 条目ID | 条目名称 | 映射适配度 |
|---|---|---|---|
| PLOVER | - | Time-of-check Time-of-use race condition | - |
| 7 Pernicious Kingdoms | - | File Access Race Conditions: TOCTOU | - |
| CLASP | - | Time of check, time of use race condition | - |
| CLASP | - | Race condition in switch | - |
| CERT C Secure Coding | FIO01-C | Be careful using functions that use file names for identification | - |
| Software Fault Patterns | SFP20 | Race Condition Window | - |
关键信息
CWE ID: CWE-367
抽象级别: Base
结构: Simple
状态: Incomplete
利用可能性: Medium