CWE-126: Buffer Over-read
The product reads from a buffer using buffer access mechanisms such as indexes or pointers that reference memory locations after the targeted buffer.
How it's found
Buffer Over-read is a specific, narrowly defined instance of a broader pattern. Testers confirm it with targeted code review and a proof-of-concept input that exercises the exact code path this weakness describes.
Vulnerable vs. safe
/* Validate number of parameters and ensure valid content */
/* copy filename parameter to variable, may cause off-by-one overflow */
/* copy pattern parameter to variable, may cause off-by-one overflow */char Filename[256];char Pattern[32];...strncpy(Filename, argv[1], sizeof(Filename));strncpy(Pattern, argv[2], sizeof(Pattern));printf("Searching file: %s for the pattern: %s\n", Filename, Pattern);Scan_File(Filename, Pattern);int main(int argc, char **argv){}/* copy filename parameter to variable, no off-by-one overflow */
/* copy pattern parameter to variable, no off-by-one overflow */
strncpy(Filename, argv[2], sizeof(Filename)-1);Filename[255]='\0';strncpy(Pattern, argv[3], sizeof(Pattern)-1);
Pattern[31]='\0';Consequences
- Read Memory
- Bypass Protection Mechanism: By reading out-of-bounds memory, an attacker might be able to get secret values, such as memory addresses, which can bypass protection mechanisms such as ASLR in order to improve the reliability and likelihood of exploiting a separate weakness to achieve code execution instead of just denial of service.
- DoS: Crash, Exit, or Restart: An attacker might be able to cause a crash or other denial of service by causing the product to read a memory location that is not allowed (such as a segmentation fault), or to cause other conditions in which the read operation returns more data than is expected.
Where this fits in a TurboPentest engagement
This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.
Frequently asked questions
What is CWE-126?
The product reads from a buffer using buffer access mechanisms such as indexes or pointers that reference memory locations after the targeted buffer.
How do you find Buffer Over-read?
Buffer Over-read is a specific, narrowly defined instance of a broader pattern. Testers confirm it with targeted code review and a proof-of-concept input that exercises the exact code path this weakness describes.
What is the impact of CWE-126?
Read Memory Bypass Protection Mechanism: By reading out-of-bounds memory, an attacker might be able to get secret values, such as memory addresses, which can bypass protection mechanisms such as ASLR in order to improve the reliability and likelihood of exploiting a separate weakness to achieve code execution instead of just denial of service. DoS: Crash, Exit, or Restart: An attacker might be able to cause a crash or other denial of service by causing the product to read a memory location that is not allowed (such as a segmentation fault), or to cause other conditions in which the read operation returns more data than is expected.
Does TurboPentest test for Buffer Over-read?
This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.
Related CWEs
Written and reviewed by
Michel Chamberland - Founder & CEO, IntegSec
CISSP, OSCP, OSCE, CEH, GIAC, CCSK · 20+ years in offensive security
Michel has spent 20+ years on offensive security teams including IBM X-Force Red and Trustwave SpiderLabs, leading penetration tests, red team engagements, and breach response for Fortune 500 customers. He is the founder of IntegSec and the architect of TurboPentest.
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