This indicates an attack attempt to exploit a Denial of Service vulnerability in OpenProject Upload Attachment.
The vulnerability is due to an error when the vulnerable software handles a maliciously crafted request. A remote attacker may be able to exploit this to cause a denial of service condition on the affected system.
OpenProject 10.1.0 and below
Denial of Service: Remote attackers can crash vulnerable systems.
Apply the most recent upgrade or patch from the vendor.