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

Description

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.

Extended Description

N/A

ThreatScore

Threat Mapped score: 0.0

Industry: Finiancial

Threat priority: Unclassified

Observed Examples (CVEs)

CVE: CVE-2021-22991 — KEV

Incorrect URI normalization in application traffic product leads to buffer overflow, as exploited in the wild per CISA KEV.
CVE: CVE-2020-29557 — KEV

Buffer overflow in Wi-Fi router web interface, as exploited in the wild per CISA KEV.
CVE: CVE-2009-2550

Classic stack-based buffer overflow in media player using a long entry in a playlist
CVE: CVE-2009-2403

Heap-based buffer overflow in media player using a long entry in a playlist
CVE: CVE-2009-0689

large precision value in a format string triggers overflow
CVE: CVE-2009-0690

negative offset value leads to out-of-bounds read
CVE: CVE-2009-1532

malformed inputs cause accesses of uninitialized or previously-deleted objects, leading to memory corruption
CVE: CVE-2009-1528

chain: lack of synchronization leads to memory corruption
CVE: 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: CVE-2009-0558

attacker-controlled array index leads to code execution
CVE: 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: CVE-2009-0566

chain: incorrect calculations lead to incorrect pointer dereference and memory corruption
CVE: CVE-2009-1350

product accepts crafted messages that lead to a dereference of an arbitrary pointer
CVE: CVE-2009-0191

chain: malformed input causes dereference of uninitialized memory
CVE: CVE-2008-4113

OS kernel trusts userland-supplied length value, allowing reading of sensitive information
CVE: 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: CVE-2003-0542

buffer overflow involving a regular expression with a large number of captures
CVE: CVE-2017-1000121

chain: unchecked message size metadata allows integer overflow (CWE-190) leading to buffer overflow (CWE-119).

Related Attack Patterns (CAPEC)

Attack TTPs

N/A

Modes of Introduction

Phase	Note
Implementation	N/A

Common Consequences

Impact: Execute Unauthorized Code or Commands, Modify Memory — Notes: 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 alter the intended control flow by redirecting 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.
Impact: Read Memory, DoS: Crash, Exit, or Restart, DoS: Resource Consumption (CPU), DoS: Resource Consumption (Memory) — Notes: 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.
Impact: Read Memory — Notes: 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 buffer's position in memory, this knowledge can be used to craft further attacks, possibly with more severe consequences.

Potential 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 a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe. (N/A)
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. (N/A)
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 [REF-1334] discusses canary-based detection in detail. (Defense in Depth)
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. (N/A)
Operation: 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]. (Defense in Depth)
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 Execution Prevention) from D3FEND [REF-1336]. (Defense in Depth)
Implementation: Replace unbounded copy functions with analogous functions that support length arguments, such as strcpy with strncpy. Create these if they are not available. (Moderate)

Applicable Platforms

C (N/A, Often)
C++ (N/A, Often)
None (Assembly, Undetermined)

Demonstrative Examples

Intro: 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.

Body: 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.

void host_lookup(char *user_supplied_addr){ struct hostent *hp; in_addr_t *addr; char hostname[64]; in_addr_t inet_addr(const char *cp); /*routine that ensures user_supplied_addr is in the right format for conversion */ validate_addr_form(user_supplied_addr); addr = inet_addr(user_supplied_addr); hp = gethostbyaddr( addr, sizeof(struct in_addr), AF_INET); strcpy(hostname, hp->h_name); }

Intro: This example applies an encoding procedure to an input string and stores it into a buffer.

Body: The programmer attempts to encode the ampersand character in the user-controlled string, however the length of the string is validated before the encoding procedure is applied. Furthermore, the programmer assumes encoding expansion will only expand a given character by a factor of 4, while the encoding of the ampersand expands by 5. As a result, when the encoding procedure expands the string it is possible to overflow the destination buffer if the attacker provides a string of many ampersands.

char * copy_input(char *user_supplied_string){ int i, dst_index; char *dst_buf = (char*)malloc(4*sizeof(char) * MAX_SIZE); if ( MAX_SIZE <= strlen(user_supplied_string) ){ die("user string too long, die evil hacker!"); } dst_index = 0; for ( i = 0; i < strlen(user_supplied_string); i++ ){ if( '&' == user_supplied_string[i] ){ dst_buf[dst_index++] = '&'; dst_buf[dst_index++] = 'a'; dst_buf[dst_index++] = 'm'; dst_buf[dst_index++] = 'p'; dst_buf[dst_index++] = ';'; } else if ('<' == user_supplied_string[i] ){ /* encode to &lt; */ } else dst_buf[dst_index++] = user_supplied_string[i]; } return dst_buf; }

Intro: The following example asks a user for an offset into an array to select an item.

Body: The programmer allows the user to specify which element in the list to select, however an attacker can provide an out-of-bounds offset, resulting in a buffer over-read (CWE-126).

int main (int argc, char **argv) { char *items[] = {"boat", "car", "truck", "train"}; int index = GetUntrustedOffset(); printf("You selected %s\n", items[index-1]); }

Intro: In the following code, the method retrieves a value from an array at a specific array index location that is given as an input parameter to the method

Body: However, this method only verifies that the given array index is less than the maximum length of the array but does not check for the minimum value (CWE-839). This will allow a negative value to be accepted as the input array index, which will result in a out of bounds read (CWE-125) and may allow access to sensitive memory. The input array index should be checked to verify that is within the maximum and minimum range required for the array (CWE-129). In this example the if statement should be modified to include a minimum range check, as shown below.

int getValueFromArray(int *array, int len, int index) { int value; // check that the array index is less than the maximum // length of the array if (index < len) { // get the value at the specified index of the array value = array[index]; } // if array index is invalid then output error message // and return value indicating error else { printf("Value is: %d\n", array[index]); value = -1; } return value; }

Intro: Windows provides the _mbs family of functions to perform various operations on multibyte strings. When these functions are passed a malformed multibyte string, such as a string containing a valid leading byte followed by a single null byte, they can read or write past the end of the string buffer causing a buffer overflow. The following functions all pose a risk of buffer overflow: _mbsinc _mbsdec _mbsncat _mbsncpy _mbsnextc _mbsnset _mbsrev _mbsset _mbsstr _mbstok _mbccpy _mbslen

Notes

Applicable Platform: It is possible in any programming languages without memory management support to attempt an operation outside of the bounds of a memory buffer, but the consequences will vary widely depending on the language, platform, and chip architecture.

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