CWE-170Improper Null Termination

Description

The product does not terminate or incorrectly terminates a string or array with a null character or equivalent terminator.

Common consequences

• Confidentiality,Integrity,Availability→Read Memory,Execute Unauthorized Code or Commands
  The case of an omitted null character is the most dangerous of the possible issues. This will almost certainly result in information disclosure, and possibly a buffer overflow condition, which may be exploited to execute arbitrary code.
• Confidentiality,Integrity,Availability→DoS: Crash, Exit, or Restart,Read Memory,DoS: Resource Consumption (CPU),DoS: Resource Consumption (Memory)
  If a null character is omitted from a string, then most string-copying functions will read data until they locate a null character, even outside of the intended boundaries of the string. This could: cause a crash due to a segmentation fault
• Integrity,Availability→Modify Memory,DoS: Crash, Exit, or Restart
  Misplaced null characters may result in any number of security problems. The biggest issue is a subset of buffer overflow, and write-what-where conditions, where data corruption occurs from the writing of a null character over valid data, o
• Integrity,Confidentiality,Availability,Access Control,Other→Alter Execution Logic,Execute Unauthorized Code or Commands
  Should the null character corrupt the process flow, or affect a flag controlling access, it may lead to logical errors which allow for the execution of arbitrary code.

Potential mitigations

• Requirements
  Use a language that is not susceptible to these issues. However, be careful of null byte interaction errors (CWE-626) with lower-level constructs that may be written in a language that is susceptible.
• Implementation
  Ensure that all string functions used are understood fully as to how they append null characters. Also, be wary of off-by-one errors when appending nulls to the end of strings.
• Implementation
  If performance constraints permit, special code can be added that validates null-termination of string buffers, this is a rather naive and error-prone solution.
• Implementation
  Switch to bounded string manipulation functions. Inspect buffer lengths involved in the buffer overrun trace reported with the defect.
• Implementation
  Add code that fills buffers with nulls (however, the length of buffers still needs to be inspected, to ensure that the non null-terminated string is not written at the physical end of the buffer).

Related CWEs

Recent CVEs classified under this CWE