This indicates an attack attempt to exploit a Denial of Service vulnerability in Apache Software Foundation Santuario XML Security for Java.
The vulnerability is due to an error in vulnerable module when validating signatures in a crafted XML file. A remote attacker may be able to exploit this to cause a denial of service condition on the affected system.
Apache Software Foundation Santuario XML Security for Java prior to 1.5.6
Denial of Service: Remote attackers can crash vulnerable systems or services
Apply the most recent upgrade or patch from the vendor.