Description
View on MITREStrategy: Language Selection Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
Strategy: Libraries or Frameworks Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega [ REF-57 ], and the Strsafe.h library from Microsoft [ REF-56 ]. These libraries provide safer versions of overflow-prone string-handling functions. Note: This is not a complete solution, since many buffer overflows are not related to strings.
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 Note: 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.
Consider adhering to the following rules when allocating and managing an application's memory: Double check that the buffer is as large as specified. When using functions that accept a number of bytes to copy, such as strncpy(), be aware that if the destination buffer size is equal to the source buffer size, it may not NULL-terminate the string. Check buffer boundaries if accessing the buffer in a loop and make sure there is no danger of writing past the allocated space. If necessary, truncate all input strings to a reasonable length before passing them to the copy and concatenation functions.
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 Note: These techniques do not provide a complete solution. For instance, exploits frequently use a bug that discloses memory addresses in order to maximize reliability of code execution [ REF-1337 ]. It has also been shown that a side-channel attack can bypass ASLR [ REF-1333 ].
Strategy: Environment Hardening Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX [ REF-60 ] [ REF-61 ]. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment. For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND [ REF-1336 ]. Effectiveness: Defense in Depth Note: This is not a complete solution, since buffer overflows could be used to overwrite nearby variables to modify the software's state in dangerous ways. In addition, it cannot be used in cases in which self-modifying code is required. Finally, an attack could still cause a denial of service, since the typical response is to exit the application.
Replace unbounded copy functions with analogous functions that support length arguments, such as strcpy with strncpy. Create these if they are not available. Effectiveness: Moderate Note: This approach is still susceptible to calculation errors, including issues such as off-by-one errors ( CWE-193 ) and incorrectly calculating buffer lengths ( CWE-131 ).
No detection method information available for this CWE.
No examples or observed CVEs available for this CWE.
CWE-787: CWE-787: Out-of-bounds Write is a Common Weakness Enumeration (CWE) entry maintained by MITRE. Description
Yes. CWE-787 ranked #2 in the CWE Top 25 for 2024, associated with 3,842 CVEs that year. The CWE Top 25 highlights the most common and impactful software weaknesses based on real-world vulnerability data.
If exploited, CWE-787 (CWE-787: Out-of-bounds Write) it can compromise Modify Memory, Execute Unauthorized Code or Commands, DoS: Crash, Exit, or Restart and Unexpected State, leading to outcomes such as Scope: Integrity Write operations could cause memory corruption. In some cases, an adversary can modify control data such as return addresses in order to execute unexpected code., Scope: Availability Attempting to access out-of-range, invalid, or unauthorized memory could cause the product to crash. and Scope: Other Subsequent write operations can produce undefined or unexpected results..
Recommended mitigations for CWE-787 include: Strategy: Language Selection Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe. Strategy: Libraries or Frameworks Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega [ REF-57 ], and the Strsafe.h library from Microsoft [ REF-56 ]. These libraries provide safer versions of overflow-prone string-handling functions. Note: This is not a complete solution, since many buffer overflows are not related to strings. 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 Note: 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.
CWE-787 commonly affects Languages. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.
A CWE (Common Weakness Enumeration) like CWE-787 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.
Search for vulnerabilities that exploit CWE-787
See how this weakness ranks against others
Understanding vulnerabilities vs weaknesses
How vulnerability severity is measured
Complete technical details and references