MCP error. fetch failed: unable to get issuer certificate

Support Bug Reports
1

Where does the bug appear (feature/product)?

  • Cursor IDE

  • Cursor CLI

  • Background Agent (GitHub, Slack, Web, Linear)

  • BugBot

  • Somewhere else…

Describe the Bug
I’m trying to connect Fibery MCP

"Fibery": {

      "url": "https://mcp-eu-svc.fibery.io/mcp"

}

but get an error typeError: fetch failed: unable to get issuer certificate

Steps to Reproduce
How can you reproduce this bug? We have a much better chance at fixing issues if we can reproduce them!

  1. open mcp.json

  2. add

"Fibery": {

      "url": "https://mcp-eu-svc.fibery.io/mcp"

}

Expected Behavior
Server should get connected

Screenshots / Screen Recordings
infinite loading tools

image
image1264×174 7.13 KB

Operating System

  • Windows 10/11

  • MacOS

  • Linux

Version Information

IDE:
Version: 2.4.21
VSCode Version: 1.105.1
Commit: dc8361355d709f306d5159635a677a571b277bc0
Date: 2026-01-22T16:57:59.675Z
Build Type: Stable
Release Track: Default
Electron: 39.2.7
Chromium: 142.0.7444.235
Node.js: 22.21.1
V8: 14.2.231.21-electron.0
OS: Darwin arm64 25.1.0

Additional Information

Here is a log I see

2026-01-23 14:00:12.446 [info] Handling CreateClient action
2026-01-23 14:00:12.447 [info] Creating streamableHttp transport
2026-01-23 14:00:12.456 [info] Handling ListOfferings action, server stored: false
2026-01-23 14:00:12.457 [info] Server creation in progress, waiting for completion
2026-01-23 14:00:12.481 [info] Handling GetInstructions action
2026-01-23 14:00:12.481 [info] Server creation in progress for getInstructions, waiting
2026-01-23 14:00:12.483 [info] Handling GetInstructions action
2026-01-23 14:00:12.483 [info] Server creation in progress for getInstructions, waiting
2026-01-23 14:00:12.547 [info] Connecting to streamableHttp server
2026-01-23 14:00:12.547 [info] No stored tokens found
2026-01-23 14:00:12.565 [info] Handling GetInstructions action
2026-01-23 14:00:12.565 [info] Server creation in progress for getInstructions, waiting
2026-01-23 14:00:12.618 [error] Client error for command fetch failed
2026-01-23 14:00:12.619 [info] Client closed for command
2026-01-23 14:00:12.619 [warning] Error connecting to streamableHttp server, falling back to SSE: fetch failed
2026-01-23 14:00:12.619 [warning] Error connecting to streamableHttp server, falling back to SSE: fetch failed
2026-01-23 14:00:12.619 [info] Connecting to SSE server
2026-01-23 14:00:12.622 [info] No stored tokens found
2026-01-23 14:00:12.630 [info] Handling GetInstructions action
2026-01-23 14:00:12.631 [info] Server creation in progress for getInstructions, waiting
2026-01-23 14:00:12.631 [info] Handling GetInstructions action
2026-01-23 14:00:12.631 [info] Server creation in progress for getInstructions, waiting
2026-01-23 14:00:12.693 [error] Client error for command SSE error: TypeError: fetch failed: unable to get issuer certificate
2026-01-23 14:00:12.693 [error] Error connecting to SSE server after fallback: SSE error: TypeError: fetch failed: unable to get issuer certificate
2026-01-23 14:00:12.693 [info] Client closed for command
2026-01-23 14:00:12.693 [warning] Pending server creation failed: SSE error: TypeError: fetch failed: unable to get issuer certificate
2026-01-23 14:00:12.710 [info] Handling GetInstructions action
2026-01-23 14:00:12.710 [error] No server info found
2026-01-23 14:00:12.710 [info] Handling GetInstructions action
2026-01-23 14:00:12.710 [error] No server info found
2026-01-23 14:00:13.098 [info] Handling GetInstructions action
2026-01-23 14:00:13.098 [error] No server info found
2026-01-23 14:00:13.102 [info] Handling ListOfferings action, server stored: false
2026-01-23 14:00:13.102 [info] Server not yet created, returning empty offerings
2026-01-23 14:00:13.203 [info] Handling GetInstructions action
2026-01-23 14:00:13.203 [error] No server info found
2026-01-23 14:00:13.735 [info] Handling GetInstructions action
2026-01-23 14:00:13.735 [error] No server info found

I know for sure that the server itself is working and guys with claude code can use it. For a moment I thought that it is some local problem and tried to debug it together with cursor. However everything seems to be fine. Here is cursor’s summary

Summary of Test Results
Based on testing, here's what we found:
✅ What Works
Direct curl connection: SSL certificate validates successfully
Node.js HTTPS connection: Certificate validates (authorized: true)
OpenSSL verification: Certificate chain complete, return code 0
Certificate: Valid GoDaddy cert for *.fibery.io, expires Apr 2026
❌ What Fails
Only Cursor's MCP extension fails with "unable to get issuer certificate"
Same error consistently across multiple attempts

Thanks in advance for any tips :man_bowing:t2:

Does this stop you from using Cursor?

  • Yes - Cursor is unusable

  • Sometimes - I can sometimes use Cursor

  • No - Cursor works, but with this issue

2

Hi there!

We detected that this may be a bug report, so we’ve moved your post to the Bug Reports category.

To help us investigate and fix this faster, could you edit your original post to include the details from the template below?

Bug Report Template - Click to expand

Where does the bug appear (feature/product)?

  • Cursor IDE
  • Cursor CLI
  • Background Agent (GitHub, Slack, Web, Linear)
  • BugBot
  • Somewhere else…

Describe the Bug
A clear and concise description of what the bug is.

Steps to Reproduce
How can you reproduce this bug? We have a much better chance at fixing issues if we can reproduce them!

  1. …
  2. …
  3. …

Expected Behavior
What is meant to happen here that isn’t working correctly?

Screenshots / Screen Recordings
If applicable, attach images or videos (.jpg, .png, .gif, .mp4, .mov)

Operating System

  • Windows 10/11
  • MacOS
  • Linux

Version Information

  • For Cursor IDE: Menu → About Cursor → Copy
  • For Cursor CLI: Run agent about in your terminal
IDE:
Version: 2.xx.x
VSCode Version: 1.105.1
Commit: ......

CLI:
CLI Version 2026.01.17-d239e66

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For AI issues: add Request ID with privacy disabled
Request ID: f9a7046a-279b-47e5-ab48-6e8dc12daba1
For Background Agent issues, also post the ID: bc-…

Additional Information
Add any other context about the problem here.

Does this stop you from using Cursor?

  • Yes - Cursor is unusable
  • Sometimes - I can sometimes use Cursor
  • No - Cursor works, but with this issue

The more details you provide, the easier it is for us to reproduce and fix the issue. Thanks!

4

Hey, thanks for the report. This is a known issue with MCP and the new Let’s Encrypt R12 certificates. I’ve seen a few reports. Cursor can’t verify these new intermediate certificates yet, even though they’re valid.

A similar case is here: Cursor seems to me missing some CA certificates? (Can't connect to some HTTPS servers)

The bug is logged, but there’s no ETA for a fix yet. Your report helps us prioritize. I’ll add that Fibery is affected too.

Sadly, there’s no workaround right now. If I find any status updates, I’ll post them here.

1 Like
5

If this is your server, LE rotates their intermediates, so requesting a new cert until the pick one that Cursor knows will mitigate this…

6

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