This problem has been recovered already.
A service disruption incident of the following details occurred.
Incident Date
- Occurred: 2025-12-28 16:11 [UTC]
- Recovered: 2026-01-05 15:37 [UTC] （7 days 23 hours 6 minutes period）
What Occurred
When sending a request in multipart/form-data format to the [Message Start Event (HTTP)], if the number of parts in the request exceeds 50, the request will not be accepted and a 500 error be returned.
Note: The number of parts is roughly corresponds to the number of request parameters, but it also includes the number of files sent for file-type data items and the number of selected options for Select-type (Checkbox) Data Items.
Cause of Trouble
We applied patch version updates to our application servers, which primarily included bug fixes and security patches, along with upgrades to versions 17.1.3 and 17.2.0. This patch introduced a restriction on the number of parts that could be included in multipart requests as a countermeasure against DoS attacks.
However, because we did not explicitly set an upper limit during the version upgrade, the default value of 50 was applied. As a result, multipart requests for [Message Start Event (HTTP)] with more than 50 parts resulted in errors.
Reaction
We performed system maintenance to increase the maximum number of parts allowed for multipart requests. While the exact limit is not disclosed, it is not unlimited and is sufficient for normal usage.