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