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Description
The code uses a variable that has not been initialized, leading to unpredictable or unintended results.
In some languages such as C and C++, stack variables are not initialized by default. They generally contain junk data with the contents of stack memory before the function was invoked. An attacker can sometimes control or read these contents. In other languages or conditions, a variable that is not explicitly initialized can be given a default value that has security implications, depending on the logic of the program. The presence of an uninitialized variable can sometimes indicate a typographic error in the code.
Modes of Introduction:
– Implementation
Likelihood of Exploit: High
Related Weaknesses
CWE-908
CWE-665
CWE-665
Consequences
Availability, Integrity, Other: Other
Initial variables usually contain junk, which can not be trusted for consistency. This can lead to denial of service conditions, or modify control flow in unexpected ways. In some cases, an attacker can “pre-initialize” the variable using previous actions, which might enable code execution. This can cause a race condition if a lock variable check passes when it should not.
Authorization, Other: Other
Strings that are not initialized are especially dangerous, since many functions expect a null at the end — and only at the end — of a string.
Potential Mitigations
Phase: Implementation
Description:
Assign all variables to an initial value.
Phase: Build and Compilation
Description:
Most compilers will complain about the use of uninitialized variables if warnings are turned on.
Phase: Implementation, Operation
Description:
When using a language that does not require explicit declaration of variables, run or compile the software in a mode that reports undeclared or unknown variables. This may indicate the presence of a typographic error in the variable’s name.
Phase: Requirements
Description:
The choice could be made to use a language that is not susceptible to these issues.
Phase: Architecture and Design
Description:
Mitigating technologies such as safe string libraries and container abstractions could be introduced.
CVE References
- CVE-2019-15900
- Chain: sscanf() call is used to check if a username and group exists, but the return value of sscanf() call is not checked (CWE-252), causing an uninitialized variable to be checked (CWE-457), returning success to allow authorization bypass for executing a privileged (CWE-863).
- CVE-2008-3688
- Chain: A denial of service may be caused by an uninitialized variable (CWE-457) allowing an infinite loop (CWE-835) resulting from a connection to an unresponsive server.
- CVE-2008-0081
- Uninitialized variable leads to code execution in popular desktop application.
- CVE-2007-4682
- Crafted input triggers dereference of an uninitialized object pointer.
- CVE-2007-3468
- Crafted audio file triggers crash when an uninitialized variable is used.
