CVE-2026-108859
mcp-go through 1.2.1 Denial of Service via Unbounded POST Body Buffering
- State
- Published
- Severity
- 8.7 High
- Published
- Oct 11, 2026
- Updated
- Oct 18, 2026
- Reserved
- Oct 11, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 8.7 High | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N | VulnCheck |
| 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | VulnCheck |
Weaknesses
- CWE-770 Allocation of Resources Without Limits or Throttling
Affected Products
| Product | Versions |
|---|---|
mcp-gomark3labs |
|
References
- https://hackmd.io/@1ExmmukzRMWN7B4gQ4W-4Q/mark3labs-mcp-go-streamable-http-unbounded-bodythird-party-advisory
- https://github.com/mark3labs/mcp-go/blob/90d247ed8d45cbb7d71d9a95e112789b78760443/server/streamable_http.go#L405-L411technical-description
- https://github.com/mark3labs/mcp-goproduct
- VulnCheck Advisory: mcp-go through 1.2.1 Denial of Service via Unbounded POST Body Bufferingthird-party-advisory
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