Weakness · High
CWE-194: Unexpected Sign Extension
What it is
The product performs an operation on a number that causes it to be sign extended when it is transformed into a larger data type. When the original number is negative, this can produce unexpected values that lead to resultant weaknesses.
- Severity (our rating)
- High
- Likelihood of exploit
- High
- Introduced during
- Implementation
- Exploited in the wild
- No CVE in CISA's catalog
What an attacker can do
- Read Memory (Integrity, Confidentiality, Availability, Other)
- Modify Memory (Integrity, Confidentiality, Availability, Other)
- Other (Integrity, Confidentiality, Availability, Other)
How to prevent it
Implementation
- Avoid using signed variables if you don't need to represent negative values. When negative values are needed, perform validation after you save those values to larger data types, or before passing them to functions that are expecting unsigned values.
How to find it
- Automated Static Analysis. Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
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Start freeSource: MITRE Common Weakness Enumeration, CWE version 4.19.1. CWE is a trademark of The MITRE Corporation.