CVE-2026-81099
MEDIUMDescription
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.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 5% of all known CVEs.
References
Related Vulnerabilities
Other CWE-346 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2025-34291 | High | 8.8 | 84% | KEV | - |
| CVE-2009-1185 | High | 7.2 | 82% | - | Fix |
| CVE-2015-4495 | High | 8.8 | 71% | KEV | Fix |
| CVE-2020-16952 | High | 8.6 | 71% | - | - |
| CVE-2023-29711 | Critical | 9.8 | 70% | - | - |
| CVE-2024-23898 | High | 8.8 | 67% | - | Fix |
Common questions
How do I fix CVE-2026-81099?
No published fix for CVE-2026-81099 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-81099 being actively exploited?
Not that we know of. CVE-2026-81099 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.16% is the estimated probability that it will be exploited in the next 30 days. That is higher than 5% of all scored CVEs.
How severe is CVE-2026-81099?
CVE-2026-81099 has a CVSS v3 base score of 6.8, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-08-27.