Signed to Unsigned Conversion Error

Opis

The product uses a signed primitive and performs a cast to an unsigned primitive, which can produce an unexpected value if the value of the signed primitive can not be represented using an unsigned primitive.

It is dangerous to rely on implicit casts between signed and unsigned numbers because the result can take on an unexpected value and violate assumptions made by the program.

Often, functions will return negative values to indicate a failure. When the result of a function is to be used as a size parameter, using these negative return values can have unexpected results. For example, if negative size values are passed to the standard memory copy or allocation functions they will be implicitly cast to a large unsigned value. This may lead to an exploitable buffer overflow or underflow condition.

Skutki

• Integrity

  Unexpected State

  Conversion between signed and unsigned values can lead to a variety of errors, but from a security standpoint is most commonly associated with integer overflow and buffer overflow vulnerabilities.

Przykłady podatności

• 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-2007-4268 Chain: integer signedness error (CWE-195) passes signed comparison, leading to heap overflow (CWE-122)

Słabość nadrzędna

• CWE-681 Incorrect Conversion between Numeric Types

Może prowadzić do

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

Kiedy powstaje

• Implementation

Dotyczy

C, C++

Źródła

1. The Art of Software Security Assessment — Mark Dowd, John McDonald, Justin Schuh, Chapter 6, "Type Conversions", Page 223, Addison Wesley, 2006
2. The CLASP Application Security Process — Secure Software, Inc., 2005