CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer
| Abstraction | Structure | Status |
|---|---|---|
| None | Simple | Stable |
Description
The product performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer.
Extended Description
Certain languages allow direct addressing of memory locations and do not automatically ensure that these locations are valid for the memory buffer that is being referenced. This can cause read or write operations to be performed on memory locations that may be associated with other variables, data structures, or internal program data.
As a result, an attacker may be able to execute arbitrary code, alter the intended control flow, read sensitive information, or cause the system to crash.
Alternate Terms
- Buffer Overflow: This term has many different meanings to different audiences. From a CWE mapping perspective, this term should be avoided where possible. Some researchers, developers, and tools intend for it to mean “write past the end of a buffer,” whereas others use the same term to mean “any read or write outside the boundaries of a buffer, whether before the beginning of the buffer or after the end of the buffer.” Still others using the same term could mean “any action after the end of a buffer, whether it is a read or write.” Since the term is commonly used for exploitation and for vulnerabilities, it further confuses things.
- buffer overrun: Some prominent vendors and researchers use the term “buffer overrun,” but most people use “buffer overflow.” See the alternate term for “buffer overflow” for context.
- memory safety: Generally used for techniques that avoid weaknesses related to memory access, such as those identified by CWE-119 and its descendants. However, the term is not formal, and there is likely disagreement between practitioners as to which weaknesses are implicitly covered by the “memory safety” term.
Related Weaknesses
| Nature | ID | View ID | Name |
|---|---|---|---|
| ChildOf | CWE-118 | 1000 | Incorrect Access of Indexable Resource (‘Range Error’) |
| ChildOf | CWE-20 | 700 | Improper Input Validation |
Modes of Introduction
| Phase | Note |
|---|---|
| Implementation | - |
Applicable Platforms
Languages
Class: None Class: None Class: Assembly
Technologies
Likelihood Of Exploit
High
Common Consequences
| Scope | Impact | Note |
|---|---|---|
| Integrity, Confidentiality, Availability | Execute Unauthorized Code or Commands, Modify Memory | If the memory accessible by the attacker can be effectively controlled, it may be possible to execute arbitrary code, as with a standard buffer overflow. If the attacker can overwrite a pointer’s worth of memory (usually 32 or 64 bits), they can redirect a function pointer to their own malicious code. Even when the attacker can only modify a single byte arbitrary code execution can be possible. Sometimes this is because the same problem can be exploited repeatedly to the same effect. Other times it is because the attacker can overwrite security-critical application-specific data – such as a flag indicating whether the user is an administrator. |
| Availability, Confidentiality | Read Memory, DoS: Crash, Exit, or Restart, DoS: Resource Consumption (CPU), DoS: Resource Consumption (Memory) | Out of bounds memory access will very likely result in the corruption of relevant memory, and perhaps instructions, possibly leading to a crash. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop. |
| Confidentiality | Read Memory | In the case of an out-of-bounds read, the attacker may have access to sensitive information. If the sensitive information contains system details, such as the current buffers position in memory, this knowledge can be used to craft further attacks, possibly with more severe consequences. |
Detection Methods
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.
Effectiveness: High
Note: Detection techniques for buffer-related errors are more mature than for most other weakness types.
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 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
Effectiveness: SOAR Partial
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
Effectiveness: SOAR Partial
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
Effectiveness: SOAR Partial
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
Effectiveness: SOAR Partial
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)
Effectiveness: SOAR Partial
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
Effectiveness: High
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.)
Effectiveness: High
Potential Mitigations
Requirements
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.
Architecture and Design
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.
Operation
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.
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.
Operation
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].
Operation
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].
Implementation
Replace unbounded copy functions with analogous functions that support length arguments, such as strcpy with strncpy. Create these if they are not available.
Observed Examples
- CVE-2021-22991: Incorrect URI normalization in application traffic product leads to buffer overflow, as exploited in the wild per CISA KEV.
- CVE-2020-29557: Buffer overflow in Wi-Fi router web interface, as exploited in the wild per CISA KEV.
- CVE-2009-2550: Classic stack-based buffer overflow in media player using a long entry in a playlist
- CVE-2009-2403: Heap-based buffer overflow in media player using a long entry in a playlist
- CVE-2009-0689: large precision value in a format string triggers overflow
- CVE-2009-0690: negative offset value leads to out-of-bounds read
- CVE-2009-1532: malformed inputs cause accesses of uninitialized or previously-deleted objects, leading to memory corruption
- CVE-2009-1528: chain: lack of synchronization leads to memory corruption
- CVE-2021-29529: Chain: machine-learning product can have a heap-based buffer overflow (CWE-122) when some integer-oriented bounds are calculated by using ceiling() and floor() on floating point values (CWE-1339)
- CVE-2009-0558: attacker-controlled array index leads to code execution
- CVE-2009-0269: chain: -1 value from a function call was intended to indicate an error, but is used as an array index instead.
- CVE-2009-0566: chain: incorrect calculations lead to incorrect pointer dereference and memory corruption
- CVE-2009-1350: product accepts crafted messages that lead to a dereference of an arbitrary pointer
- CVE-2009-0191: chain: malformed input causes dereference of uninitialized memory
- CVE-2008-4113: OS kernel trusts userland-supplied length value, allowing reading of sensitive information
- CVE-2005-1513: Chain: integer overflow in securely-coded mail program leads to buffer overflow. In 2005, this was regarded as unrealistic to exploit, but in 2020, it was rediscovered to be easier to exploit due to evolutions of the technology.
- CVE-2003-0542: buffer overflow involving a regular expression with a large number of captures
- CVE-2017-1000121: chain: unchecked message size metadata allows integer overflow (CWE-190) leading to buffer overflow (CWE-119).