Book a Security Review

Weakness · High

CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer

What it is

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

Likelihood of exploit: High88 exploited in the wildMITRE CWE 4.19.1

Severity (our rating)
High
Likelihood of exploit
High
Introduced during
Implementation
Exploited in the wild
88 known exploited CVEs

What an attacker can do

  • Execute Unauthorized Code or Commands (Integrity, Confidentiality, Availability)
  • Modify Memory (Integrity, Confidentiality, Availability)
  • Read Memory (Availability, Confidentiality)
  • DoS: Crash, Exit, or Restart (Availability, Confidentiality)
  • DoS: Resource Consumption (CPU) (Availability, Confidentiality)
  • DoS: Resource Consumption (Memory) (Availability, Confidentiality)

How to prevent it

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 a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.

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, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.

Operation

  • 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 discusses canary-based detection in detail.
  • 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) and Position-Independent Executables (PIE). 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) 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.
  • 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. 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.

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 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.
  • Replace unbounded copy functions with analogous functions that support length arguments, such as strcpy with strncpy. Create these if they are not available.

How to find it

  • Automated Static Analysis. This weakness can often be detected using automated static analysis tools. Many modern tools use data flow analysis or constraint-based techniques to minimize the number of false positives. Automated static analysis generally does not account for environmental considerations when reporting out-of-bounds memory operations. This can make it difficult for users to determine which warnings should be investigated first. For example, an analysis tool might report buffer overflows that originate from command line arguments in a program that is not expected to run with setuid or other special privileges.
  • Automated Dynamic Analysis. This weakness can be detected using dynamic tools and techniques that interact with the software using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results.
  • Automated Dynamic Analysis. Use tools that are integrated during compilation to insert runtime error-checking mechanisms related to memory safety errors, such as AddressSanitizer (ASan) for C/C++.
  • Automated Static Analysis - Binary or Bytecode. According to SOAR, the following detection techniques may be useful: Cost effective for partial coverage: Binary / Bytecode Quality Analysis Bytecode Weakness Analysis - including disassembler + source code weakness analysis Binary Weakness Analysis - including disassembler + source code weakness analysis
  • Manual Static Analysis - Binary or Bytecode. According to SOAR, the following detection techniques may be useful: Cost effective for partial coverage: Binary / Bytecode disassembler - then use manual analysis for vulnerabilities & anomalies
  • Dynamic Analysis with Automated Results Interpretation. According to SOAR, the following detection techniques may be useful: Cost effective for partial coverage: Web Application Scanner Web Services Scanner Database Scanners
  • Dynamic Analysis with Manual Results Interpretation. According to SOAR, the following detection techniques may be useful: Cost effective for partial coverage: Fuzz Tester Framework-based Fuzzer
  • Manual Static Analysis - Source Code. According to SOAR, the following detection techniques may be useful: Cost effective for partial coverage: Focused Manual Spotcheck - Focused manual analysis of source Manual Source Code Review (not inspections)
  • Automated Static Analysis - Source Code. According to SOAR, the following detection techniques may be useful: Highly cost effective: Source code Weakness Analyzer Context-configured Source Code Weakness Analyzer Cost effective for partial coverage: Source Code Quality Analyzer
  • Architecture or Design Review. According to SOAR, the following detection techniques may be useful: Highly cost effective: Formal Methods / Correct-By-Construction Cost effective for partial coverage: Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)

CWE-119 on MITRE's CWE site

Exploited in the wild: 88 CVEs

Vulnerabilities caused by CWE-119 that attackers have used, from CISA's Known Exploited Vulnerabilities catalog, newest first.

All known exploited vulnerabilities

H2 Security

Found it in your code?

We review where it appears, fix it with your team, and check it was not already used against you.

Talk to our team

T Academy

Stop writing it in the first place

Learn to build software and systems without weaknesses like this one, with practice on real hosts in your browser, every objective checked on the machine.

Start free

Source: MITRE Common Weakness Enumeration, CWE version 4.19.1. CWE is a trademark of The MITRE Corporation.