CVE-2026-68497: jackson-databind: Duration XMLGregorianCalendar Unbounded Number Parse DoS

jackson-databind 3.2.1 deserializes a JSON string bound to a javax.xml.datatype.Duration or javax.xml.datatype.XMLGregorianCalendar field by passing the raw string verbatim to DatatypeFactory.newDuration(value) / newXMLGregorianCalendar(value). Per the XML-Schema lexical grammar these factory methods accept numeric components of arbitrary length, which the JDK materializes into java.math.BigInteger / BigDecimal using the native BigInteger(String) constructor (an O(n²) parser). Because the digits reside inside a JSON string token, jackson-core’s StreamReadConstraints.maxNumberLength guard (which bounds only JSON number tokens) never fires, so there is no length limit anywhere on this path. An unauthenticated attacker can submit a single small request (e.g. ~1–5 MB) that forces tens of seconds to minutes of single-thread CPU consumption, yielding a denial of service under the default JsonMapper.builder().build() mapper with no polymorphic typing or special configuration.