Integer Overflow or Wraparound

Opis

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

Inne nazwy

Overflow

The terms "overflow" and "wraparound" are used interchangeably by some people, but they can have more precise distinctions by others. See Terminology Notes.

Wraparound

The terms "overflow" and "wraparound" are used interchangeably by some people, but they can have more precise distinctions by others. See Terminology Notes.

wrap, wrap-around, wrap around

Alternate spellings of "wraparound"

Skutki

• Availability

  DoS: Crash, Exit, or Restart; DoS: Resource Consumption (Memory); DoS: Instability

  This weakness can generally lead to undefined behavior and therefore crashes. When the calculated result is used for resource allocation, this weakness can cause too many (or too few) resources to be allocated, possibly enabling crashes if the product requests more resources than can be provided.

• Integrity

  Modify Memory

  If the value in question is important to data (as opposed to flow), simple data corruption has occurred. Also, if the overflow/wraparound results in other conditions such as buffer overflows, further memory corruption may occur.

• Confidentiality, Availability, Access Control

  Execute Unauthorized Code or Commands; Bypass Protection Mechanism

  This weakness can sometimes trigger buffer overflows, which can be used to execute arbitrary code. This is usually outside the scope of the product's implicit security policy.

• Availability, Other

  Alter Execution Logic; DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU)

  If the overflow/wraparound occurs in a loop index variable, this could cause the loop to terminate at the wrong time - too early, too late, or not at all (i.e., infinite loops). With too many iterations, some loops could consume too many resources such as memory, file handles, etc., possibly leading to a crash or other DoS.

• Access Control

  Bypass Protection Mechanism

  If integer values are used in security-critical decisions, such as calculating quotas or allocation limits, integer overflows can be used to cause an incorrect security decision.

Zapobieganie

• Requirements

  Ensure that all protocols are strictly defined, such that all out-of-bounds behavior can be identified simply, and require strict conformance to the protocol.

• Requirements · Language Selection

  Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

  If possible, choose a language or compiler that performs automatic bounds checking.

• Architecture and Design · 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 [REF-1482].

  Use libraries or frameworks that make it easier to handle numbers without unexpected consequences.

  Examples include safe integer handling packages such as SafeInt (C++) or IntegerLib (C or C++). [REF-106]

• Implementation · Input Validation

  Perform input validation on any numeric input by ensuring that it is within the expected range. Enforce that the input meets both the minimum and maximum requirements for the expected range.

  Use unsigned integers where possible. This makes it easier to perform validation for integer overflows. When signed integers are required, ensure that the range check includes minimum values as well as maximum values.

• Implementation

  Understand the programming language's underlying representation and how it interacts with numeric calculation (CWE-681). Pay close attention to byte size discrepancies, precision, signed/unsigned distinctions, truncation, conversion and casting between types, "not-a-number" calculations, and how the language handles numbers that are too large or too small for its underlying representation. [REF-7]

  Also be careful to account for 32-bit, 64-bit, and other potential differences that may affect the numeric representation.

• Architecture and Design

  For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.

• Implementation · Compilation or Build Hardening

  Examine compiler warnings closely and eliminate problems with potential security implications, such as signed / unsigned mismatch in memory operations, or use of uninitialized variables. Even if the weakness is rarely exploitable, a single failure may lead to the compromise of the entire system.

Przykłady podatności

• CVE-2025-46687 Chain: Javascript engine code does not perform a length check (CWE-1284) leading to integer overflow (CWE-190) causing allocation of smaller buffer than expected (CWE-131) resulting in a heap-based buffer overflow (CWE-122)
• 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), causing too small of a buffer (CWE-131), leading to an out-of-bounds write (CWE-787).
• CVE-2021-43537 Chain: in a web browser, an unsigned 64-bit integer is forcibly cast to a 32-bit integer (CWE-681) and potentially leading to an integer overflow (CWE-190). If an integer overflow occurs, this can cause heap memory corruption (CWE-122)
• CVE-2019-19911 Chain: Python library does not limit the resources used to process images that specify a very large number of bands (CWE-1284), leading to excessive memory consumption (CWE-789) or an integer overflow (CWE-190).
• CVE-2022-0545 Chain: 3D renderer has an integer overflow (CWE-190) leading to write-what-where condition (CWE-123) using a crafted image.
• CVE-2021-30860 Chain: improper input validation (CWE-20) leads to integer overflow (CWE-190) in mobile OS, as exploited in the wild per CISA KEV.
• CVE-2021-30663 Chain: improper input validation (CWE-20) leads to integer overflow (CWE-190) in mobile OS, as exploited in the wild per CISA KEV.
• CVE-2018-10887 Chain: unexpected sign extension (CWE-194) leads to integer overflow (CWE-190), causing an out-of-bounds read (CWE-125)
• 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-2010-1866 Chain: integer overflow (CWE-190) causes a negative signed value, which later bypasses a maximum-only check (CWE-839), leading to heap-based buffer overflow (CWE-122).
• CVE-2010-2753 Chain: integer overflow leads to use-after-free
• 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-2002-0391 Integer overflow via a large number of arguments.
• CVE-2002-0639 Integer overflow in OpenSSH as listed in the demonstrative examples.
• CVE-2005-1141 Image with large width and height leads to integer overflow.
• CVE-2005-0102 Length value of -1 leads to allocation of 0 bytes and resultant heap overflow.
• CVE-2004-2013 Length value of -1 leads to allocation of 0 bytes and resultant heap overflow.
• CVE-2017-1000121 chain: unchecked message size metadata allows integer overflow (CWE-190) leading to buffer overflow (CWE-119).
• CVE-2013-1591 Chain: an integer overflow (CWE-190) in the image size calculation causes an infinite loop (CWE-835) which sequentially allocates buffers without limits (CWE-1325) until the stack is full.

Słabość nadrzędna

• CWE-682 Incorrect Calculation
• CWE-20 Improper Input Validation

Może prowadzić do

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

Słabości podrzędne

• CWE-680 Integer Overflow to Buffer Overflow

Kiedy powstaje

• Implementation — This weakness may become security critical when determining the offset or size in behaviors such as memory allocation, copying, and concatenation.

Dotyczy

Not Language-Specific, C, Not Technology-Specific

Uwagi

Integer overflows can be primary to buffer overflows when they cause less memory to be allocated than expected.

"Integer overflow" is sometimes used to cover several types of errors, including signedness errors, or buffer overflows that involve manipulation of integer data types instead of characters. Part of the confusion results from the fact that 0xffffffff is -1 in a signed context. Other confusion also arises because of the role that integer overflows have in chains.

A "wraparound" is a well-defined, standard behavior that follows specific rules for how to handle situations when the intended numeric value is too large or too small to be represented, as specified in standards such as C11.

"Overflow" is sometimes conflated with "wraparound" but typically indicates a non-standard or undefined behavior.

The "overflow" term is sometimes used to indicate cases where either the maximum or the minimum is exceeded, but others might only use "overflow" to indicate exceeding the maximum while using "underflow" for exceeding the minimum.

Some people use "overflow" to mean any value outside the representable range - whether greater than the maximum, or less than the minimum - but CWE uses "underflow" for cases in which the intended result is less than the minimum.

See [REF-1440] for additional explanation of the ambiguity of terminology.

While there may be circumstances in which the logic intentionally relies on wrapping - such as with modular arithmetic in timers or counters - it can have security consequences if the wrap is unexpected. This is especially the case if the integer overflow can be triggered using user-supplied inputs.

Źródła

1. An overview of common programming security vulnerabilities and possible solutions — Yves Younan, Student thesis section 5.4.3, 2003
2. Basic Integer Overflows — blexim, Phrack - Issue 60, Chapter 10, 2002
3. Writing Secure Code — Michael Howard, David LeBlanc, Chapter 20, "Integer Overflows" Page 620, Microsoft Press, 2002
4. 24 Deadly Sins of Software Security — Michael Howard, David LeBlanc, John Viega, "Sin 7: Integer Overflows." Page 119, McGraw-Hill, 2010
5. SafeInt — David LeBlanc, Niels Dekker
6. Top 25 Series - Rank 17 - Integer Overflow Or Wraparound — Johannes Ullrich, SANS Software Security Institute, 2010
7. The Art of Software Security Assessment — Mark Dowd, John McDonald, Justin Schuh, Chapter 6, "Signed Integer Boundaries", Page 220, Addison Wesley, 2006
8. Integer overflow — Definition variations and ambiguity, Wikipedia, 2024
9. State-of-the-Art Resources (SOAR) for Software Vulnerability Detection, Test, and Evaluation — Gregory Larsen, E. Kenneth Hong Fong, David A. Wheeler, Rama S. Moorthy, 2014
10. D3FEND: D3-TL Trusted Library — D3FEND