---
id: CVE-2026-81099
title: >-
  tiger-slack started its MCP HTTP transport without enabling the host
  allow-list the underlying SDK provides
summary: >-
  tiger-slack started its MCP HTTP transport without enabling the host
  allow-list the underlying SDK provides. mcp/src/httpServer.ts called the
  shared httpServerFactory helper and never set the DNS-rebinding-protection
  option, so the trans…
severity: medium
cvss: 6.8
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N'
cwe:
  - CWE-346
published: '2026-08-27'
updated: '2026-09-23'
sourceUpdated: '2026-09-23T17:17:42.577'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-81099'
references:
  - url: 'https://github.com/timescale/tiger-slack'
    label: disclosure@vulncheck.com
  - url: 'https://github.com/timescale/tiger-slack/pull/146'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/timescale-tiger-slack-dns-rebinding-via-disabled-host-header-allow-list
    label: disclosure@vulncheck.com
tags:
  - nvd
epss: 0.0016
epssPercentile: 0.05619
ingestedAt: '2026-09-23T17:28:14.807Z'
---

## Overview

tiger-slack started its MCP HTTP transport without enabling the host allow-list the underlying SDK provides. mcp/src/httpServer.ts called the shared httpServerFactory helper and never set the DNS-rebinding-protection option, so the transport accepted a request whatever host it named, and a page in a browser could point a name it controlled at the address the server was bound to and drive the locally reachable Slack MCP server through the visitor's browser. The fix passes the option explicitly alongside a dependency update; the update alone would not have closed it. The repository publishes no release that brackets the fix, so the affected boundary is the commit preceding it.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.