121

Modify Memory; DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory)

Modify Memory; Execute Unauthorized Code or Commands; Bypass Protection Mechanism

Modify Memory; Execute Unauthorized Code or Commands; Bypass Protection Mechanism; Other

Operation; Build and Compilation

Strategy: Environment Hardening

Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.

D3-SFCV (Stack Frame Canary Validation) from D3FEND [ REF-1334 ] discusses canary-based detection in detail.

Effectiveness: Defense in Depth

This is not necessarily a complete solution, since these mechanisms only detect certain types of overflows. In addition, the result is still a denial of service, since the typical response is to exit the application.

Architecture and Design

Operation; Build and Compilation

Strategy: Environment Hardening

Run or compile the software using features or extensions that randomly arrange the positions of a program's executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.

Examples include Address Space Layout Randomization (ASLR) [ REF-58 ] [ REF-60 ] and Position-Independent Executables (PIE) [ REF-64 ]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as "rebasing" (for Windows) and "prelinking" (for Linux) [ REF-1332 ] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.

For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [ REF-1335 ].

Effectiveness: Defense in Depth

Class: Memory-Unsafe (Often Prevalent)

C++ (Often Prevalent)

Class: Not Technology-Specific (Undetermined Prevalence)

While buffer overflow examples can be rather complex, it is possible to have very simple, yet still exploitable, stack-based buffer overflows:

The buffer size is fixed, but there is no guarantee the string in argv[1] will not exceed this size and cause an overflow.

This example takes an IP address from a user, verifies that it is well formed and then looks up the hostname and copies it into a buffer.

This function allocates a buffer of 64 bytes to store the hostname, however there is no guarantee that the hostname will not be larger than 64 bytes. If an attacker specifies an address which resolves to a very large hostname, then the function may overwrite sensitive data or even relinquish control flow to the attacker.

Note that this example also contains an unchecked return value ( CWE-252 ) that can lead to a NULL pointer dereference ( CWE-476 ).

Note: this is a curated list of examples for users to understand the variety of ways in which this weakness can be introduced. It is not a complete list of all CVEs that are related to this CWE entry.

Automated Static Analysis

Automated Dynamic Analysis

Effectiveness: Moderate