Tag Archives: Incorrect Calculation of Multi-Byte String Length

CWE-135 – Incorrect Calculation of Multi-Byte String Length

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Description

The software does not correctly calculate the length of strings that can contain wide or multi-byte characters.

Modes of Introduction:

– Implementation

 

 

Related Weaknesses

CWE-682

 

Consequences

Integrity, Confidentiality, Availability: Execute Unauthorized Code or Commands

This weakness may lead to a buffer overflow. Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of a program’s implicit security policy. This can often be used to subvert any other security service.

Availability, Confidentiality: Read Memory, DoS: Crash, Exit, or Restart, DoS: Resource Consumption (CPU), DoS: Resource Consumption (Memory)

Out of bounds memory access will very likely result in the corruption of relevant memory, and perhaps instructions, possibly leading to a crash. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop.

Confidentiality: Read Memory

In the case of an out-of-bounds read, the attacker may have access to sensitive information. If the sensitive information contains system details, such as the current buffers position in memory, this knowledge can be used to craft further attacks, possibly with more severe consequences.

 

Potential Mitigations

Phase: Implementation

Description: 

Always verify the length of the string unit character.

Phase: Implementation

Description: 

Use length computing functions (e.g. strlen, wcslen, etc.) appropriately with their equivalent type (e.g.: byte, wchar_t, etc.)

CVE References