upstream sent invalid header: "x-correlation-id\x20..." while reading response header from upstream

[sanjay-raj5]

All,
I am using ingress-nginx-controller-v1.12.0 in my cluster.Earlier we were on 1.1.0 version.
Error:
2025/01/21 14:14:15 [error] 3509#3509: *8465327 upstream sent invalid header: "x-correlation-id\x20..." while reading response header from upstream, client: 172.xx.xx.xxx, server: api.test.xyz.com, request: "POST /<my_path> HTTP/1.1", upstream: "http://172.xx.xx.xxx:8081/<my_path>", host: "api.test.xyz.com"

When checking the application, it gives me 200 SUCCESS and even tried to port-forward svc and that is also working, but with ingress, getting this error post upgrade.

Upon reverting back to 1.1.0, the same payload gives me 200 SUCCESS.

Please help me on the same

[AlexFenlon]

answer for this here: #7197