Potentially unsafe use of strcat¶
ID: cpp/unsafe-strcat
Kind: problem
Security severity: 9.8
Severity: warning
Precision: medium
Tags:
- reliability
- correctness
- security
- external/cwe/cwe-676
- external/cwe/cwe-120
- external/cwe/cwe-251
Query suites:
- cpp-security-extended.qls
- cpp-security-and-quality.qls
Click to see the query in the CodeQL repository
The standard library function strcat appends a source string to a target string. If you do not check the size of the source string then you cannot guarantee that appending the data to the target string will not cause a buffer overflow. Buffer overflows can lead to anything from a segmentation fault to a security vulnerability.
Recommendation¶
Check the highlighted function calls carefully to ensure that no buffer overflow is possible. For a more robust solution, consider adding explicit range checks or using the strncat function instead.
Example¶
void f(char *s) {
char buf[80];
strcpy(buf, "s: ");
strcat(buf, s); // wrong: buffer not checked before strcat
}
void g(char *s) {
char buf[80];
strcpy(buf, "s: ");
if(strlen(s) < 77)
strcat(buf, s); // correct: buffer size checked before strcat
}
References¶
I. Gerg, An Overview and Example of the Buffer-Overflow Exploit. IANewsletter vol 7, no 4, 2005.
M. Donaldson, Inside the Buffer Overflow Attack: Mechanism, Method & Prevention. SANS Institute InfoSec Reading Room. 2002.
Common Weakness Enumeration: CWE-676.
Common Weakness Enumeration: CWE-120.
Common Weakness Enumeration: CWE-251.