Goal Reached Thanks to every supporter — we hit 100%!

Goal: 1000 CNY · Raised: 1000 CNY

100.0%
Buy Us a Coffee

CWE-786 (在缓冲区起始位置之前访问内存) — Vulnerability Class 3

3 vulnerabilities classified as CWE-786 (在缓冲区起始位置之前访问内存). AI Chinese analysis included.

CWE-786 represents a critical memory safety weakness where software accesses memory locations preceding the start of a defined buffer. This vulnerability typically arises from improper pointer arithmetic, such as decrementing an index below zero or calculating offsets that fall outside the allocated memory bounds. Attackers exploit this flaw to read sensitive data from adjacent memory regions or write malicious code into unauthorized areas, potentially leading to information disclosure, application crashes, or arbitrary code execution. To mitigate this risk, developers must implement rigorous bounds checking before any memory access operation. Utilizing safe programming languages with automatic memory management, employing static analysis tools to detect out-of-bounds errors, and validating all pointer calculations are essential practices. Ensuring that indices remain within valid limits prevents unauthorized memory access and strengthens the overall integrity of the application against buffer-related exploits.

MITRE CWE Description
The product reads or writes to a buffer using an index or pointer that references a memory location prior to the beginning of the buffer. This typically occurs when a pointer or its index is decremented to a position before the buffer, when pointer arithmetic results in a position before the beginning of the valid memory location, or when a negative index is used.
Common Consequences (3)
ConfidentialityRead Memory
For an out-of-bounds read, the attacker may have access to sensitive information. If the sensitive information contains system details, such as the current buffer's position in memory, this knowledge can be used to craft further attacks, possibly with more severe consequences.
Integrity, AvailabilityModify Memory, DoS: Crash, Exit, or Restart
Out of bounds memory access will very likely result in the corruption of relevant memory, and perhaps instructions, possibly leading to a crash.
IntegrityModify Memory, Execute Unauthorized Code or Commands
If the corrupted memory can be effectively controlled, it may be possible to execute arbitrary code. If the corrupted memory is data rather than instructions, the system will continue to function with improper changes, possibly in violation of an implicit or explicit policy.
Examples (2)
In the following C/C++ example, a utility function is used to trim trailing whitespace from a character string. The function copies the input string to a local character string and uses a while statement to remove the trailing whitespace by moving backward through the string and overwriting whitespace with a NUL character.
char* trimTrailingWhitespace(char *strMessage, int length) { char *retMessage; char *message = malloc(sizeof(char)*(length+1)); // copy input string to a temporary string char message[length+1]; int index; for (index = 0; index < length; index++) { message[index] = strMessage[index]; } message[index] = '\0'; // trim trailing whitespace int len = index-1; while (isspace(message[len])) { message[len] = '\0'; len--; } // return string without trailing whitespace retMessage = message; return retMessage; }
Bad · C
The following example asks a user for an offset into an array to select an item.
int main (int argc, char **argv) { char *items[] = {"boat", "car", "truck", "train"}; int index = GetUntrustedOffset(); printf("You selected %s\n", items[index-1]); }
Bad · C
CVE IDTitleCVSSSeverityPublished
CVE-2026-20058 Cisco Secure Firewall Threat Defense Software Snort 3 Visual Basic for Application Denial of Service Vulnerability — Cisco Secure Firewall Threat Defense (FTD) Software 5.8 Medium2026-03-04
CVE-2022-0522 Access of Memory Location Before Start of Buffer in radareorg/radare2 — radareorg/radare2 7.1 -2022-02-08
CVE-2022-0351 Access of Memory Location Before Start of Buffer in vim/vim — vim/vim 7.8 -2022-01-25

Vulnerabilities classified as CWE-786 (在缓冲区起始位置之前访问内存) represent 3 CVEs. The CWE taxonomy describes the weakness; review individual CVEs for product-specific impact.