CWE WEAKNESSES  /  CWE-787

CWE-787

Out-of-bounds Write

What it is

The product writes data past the end, or before the beginning, of the intended buffer.

Impact

Mitigations

• [Requirements]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
• [Architecture and Design]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.
• [Operation, Build and Compilation]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] dis
• [Implementation]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 accessi
• [Operation, Build and Compilation]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]. Im
• [Operation]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
• [Implementation] Replace unbounded copy functions with analogous functions that support length arguments, such as strcpy with strncpy. Create these if they are not available.

Real-world CVE examples

• CVE-2025-27363 — Font rendering library does not properly handle assigning a signed short value to an unsigned long (CWE-195), leading to an integer wraparound (CWE-190), causin
• CVE-2023-1017 — The reference implementation code for a Trusted Platform Module does not implement length checks on data, allowing for an attacker to write 2 bytes past the end
• CVE-2021-21220 — Chain: insufficient input validation (CWE-20) in browser allows heap corruption (CWE-787), as exploited in the wild per CISA KEV.
• CVE-2021-28664 — GPU kernel driver allows memory corruption because a user can obtain read/write access to read-only pages, as exploited in the wild per CISA KEV.
• CVE-2020-17087 — Chain: integer truncation (CWE-197) causes small buffer allocation (CWE-131) leading to out-of-bounds write (CWE-787) in kernel pool, as exploited in the wild p
• CVE-2020-1054 — Out-of-bounds write in kernel-mode driver, as exploited in the wild per CISA KEV.
• CVE-2020-0041 — Escape from browser sandbox using out-of-bounds write due to incorrect bounds check, as exploited in the wild per CISA KEV.
• CVE-2020-0968 — Memory corruption in web browser scripting engine, as exploited in the wild per CISA KEV.
• CVE-2020-0022 — chain: mobile phone Bluetooth implementation does not include offset when calculating packet length (CWE-682), leading to out-of-bounds write (CWE-787)
• CVE-2019-1010006 — Chain: compiler optimization (CWE-733) removes or modifies code used to detect integer overflow (CWE-190), allowing out-of-bounds write (CWE-787).
• CVE-2009-1532 — malformed inputs cause accesses of uninitialized or previously-deleted objects, leading to memory corruption
• CVE-2009-0269 — chain: -1 value from a function call was intended to indicate an error, but is used as an array index instead.

Related weaknesses

Source: MITRE CWE. View on cwe.mitre.org →