Resource exhaustion in Mark3labs Mcp-Go
CVE-2026-108859
mcp-go through 1.2.1 contains a denial of service vulnerability in StreamableHTTPServer.ServeHTTP that allows remote unauthenticated attackers to exhaust memory by sending oversized POST bodies. Attackers can send arbitrarily large or many concurrent POST requests, read fully via io.ReadAll before validation, to degrade or OOM-kill the server process.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- hackmd.io/@1ExmmukzRMWN7B4gQ4W-4Q/mark3labs-mcp-go-streamable-http-unbounded-bo… (third-party-advisory)
- github.com/mark3labs/mcp-go/blob/90d247ed8d45cbb7d71d9a95e112789b78760443/serve… (technical-description)
- github.com/mark3labs/mcp-go (product)
- www.vulncheck.com/advisories/mcp-go-through-1.2.1-denial-of-service-via-unbound… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-108859?
- CVE-2026-108859 is a high-severity vulnerability in Mark3labs Mcp-Go, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 7.5/10. Published 2026-10-11.
- How severe is CVE-2026-108859?
- High severity. CVSS v3 base score is 7.5 out of 10.