6.8mediumMedium

CVE-2026-81099

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.

What the metrics mean

  • It is reachable over a network, without needing local access.
  • For an attacker who can reach it, exploitation depends on conditions outside the attacker's control.
  • To exploit it, no account is needed.
  • Beyond that, someone has to be persuaded to take an action first.

Scoring

CVSS
6.8 (v3.1)
Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
CVSS v4
7.6
Weakness
CWE-346
Assigned by
disclosure@vulncheck.com

Dates

Published
2026-08-27
Last modified
2026-08-27
Sources
NVD

References