CodeQL documentation

No space for zero terminator

ID: cpp/no-space-for-terminator
Kind: problem
Severity: error
Precision: high
   - reliability
   - security
   - external/cwe/cwe-131
   - external/cwe/cwe-120
   - external/cwe/cwe-122
Query suites:
   - cpp-code-scanning.qls
   - cpp-security-extended.qls
   - cpp-security-and-quality.qls

Click to see the query in the CodeQL repository

This rule identifies calls to malloc that call strlen to determine the required buffer size, but do not allocate space for the zero terminator.


The expression highlighted by this rule creates a buffer that is of insufficient size to contain the data being copied. This makes the code vulnerable to buffer overflow which can result in anything from a segmentation fault to a security vulnerability (particularly if the array is on stack-allocated memory).

Increase the size of the buffer being allocated by one or replace malloc, strcpy pairs with a call to strdup


void flawed_strdup(const char *input)
	char *copy;

	/* Fail to allocate space for terminating '\0' */
	copy = (char *)malloc(strlen(input));
	strcpy(copy, input);
	return copy;