CWE WEAKNESSES / CWE-195
CWE-195
Signed to Unsigned Conversion Error
What it is
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.
Impact
| Integrity | Unexpected State |
Real-world CVE examples
- 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), causin
- CVE-2007-4268 — Chain: integer signedness error (CWE-195) passes signed comparison, leading to heap overflow (CWE-122)
Related weaknesses
Browse all common weaknesses, check related exploited CVEs, or map to ATT&CK techniques.
Source: MITRE CWE. View on cwe.mitre.org →