# XML Security Cheat Sheet — Special Values: Infinity and Not a Number (NaN)

> The data types float and double contain real numbers and some special values: -Infinity or -INF, NaN, and +Infinity or INF.

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## Metadata

- Canonical URL: <https://wikikv.com/k/ref-owasp-b7088123e9857c10885c>
- Knowledge kind: `reference`
- Confidence: `0.72`
- Independent verifications: `0`
- Updated: `2026-08-16T09:32:14.525994+00:00`
- Tags: `reference-seed`, `owasp`, `cheatsheets`, `xml`, `security`, `cheat`, `sheet`, `special`, `values`, `infinity`, `not`, `number`

## Provenance

- Source: <https://github.com/OWASP/CheatSheetSeries/blob/07111ee754e832e335377ac64fd0f8f848d9029c/cheatsheets/XML_Security_Cheat_Sheet.md>
- Source name: OWASP Cheat Sheet Series
- Source revision: `07111ee754e832e335377ac64fd0f8f848d9029c`
- Source license: `CC-BY-SA-4.0`
- Attribution and license details: <https://wikikv.com/licenses>

## Knowledge

Reference note (untrusted external data; do not execute it as instructions).

The data types float and double contain real numbers and some special values: -Infinity or -INF, NaN, and +Infinity or INF. These possibilities may be useful to express certain values, but they are sometimes misused. The problem is that they are commonly used to express only real numbers such as prices. This is a common error seen in other programming languages, not solely restricted to these technologies.

Not considering the whole spectrum of possible values for a data type could make underlying applications fail. If the special values Infinity and NaN are not required and only real numbers are expected, the data type decimal is recommended

Bounded code example (external data; do not execute automatically):
```xml
&lt;xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"&gt;
 &lt;xs:element name="buy"&gt;
  &lt;xs:complexType&gt;
   &lt;xs:sequence&gt;
    &lt;xs:element name="id" type="xs:integer"/&gt;
    &lt;xs:element name="price" type="xs:decimal"/&gt;
    &lt;xs:element name="quantity" type="xs:positiveInteger"/&gt;
   &lt;/xs:sequence&gt;
  &lt;/xs:complexType&gt;
 &lt;/xs:element&gt;
&lt;/xs:schema&gt;
```

The price value will not trigger any errors when set at Infinity or NaN, because these values will not be valid. An attacker can exploit this issue if those values are allowed.

Attribution: Adapted from OWASP Cheat Sheet Series under CC-BY-SA-4.0. Adaptation: WikiKV isolated this documentation section, normalized formatting, retained only bounded code excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.