TLS handshake EOF when connecting to private IBM WebSphere endpoint (works when SSL verification disabled)

Description

I’m experiencing a TLS connection error when trying to send a request to a private internal service through VPN.

The service is hosted on an internal IBM WebSphere environment. The endpoint works correctly in other API clients such as Postman and Bruno.

In Bruno, the request only works when SSL/TLS Certificate Verification is disabled. If it is enabled, the request fails with a TLS error.

In Yaak, I also disabled “Validate TLS certificates”, but the request still fails with the same TLS handshake error.

Yaak fails to send the request even when trying to connect to the same endpoint.

For security reasons I cannot share the exact URL because it is a private internal endpoint.

Error

Request: https://xxx.xxx.xxx.xxx:xxxx/dev/serv/com.xxx.xxxxx.xxxxxx

Failed to send request:

Client error: reqwest::Error { kind: Request, source: hyper_util::client::legacy::Error( Connect, Custom { kind: Other, error: Custom { kind: UnexpectedEof, error: “tls handshake eof” } } ) }

Steps to Reproduce

1. Connect to a corporate VPN
2. Send a request to a private HTTPS endpoint (server TLSV1.0) hosted on IBM WebSphere
3. Disable “Validate TLS certificates” in Yaak
4. Attempt the request from Yaak
5. The TLS handshake fails with the error above

Expected Behavior

The request should succeed when TLS certificate validation is disabled, similar to other API clients.

Actual Behavior

The request fails with a TLS handshake EOF error even when “Validate TLS certificates” is disabled.

Environment

• Yaak version: Release 2026.3.1
• OS: macOS Tahoe 26.3.1 arm64
• VPN: FortiClient
• Target service: internal IBM WebSphere HTTPS endpoint

Additional Notes

• The same request works correctly in Postman.
• In Bruno it only works if SSL/TLS certificate verification is disabled.
• In Yaak the same configuration (Validate TLS certificates disabled) still results in the TLS handshake error.
• This suggests the server might be using a self-signed certificate or an internal CA.