CVE-2026-108859mcp-go through 1.2.1 Denial of Service via Unbounded POST Body Buffering
Updated under an hour ago ()
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It affects mark3labs mcp-go. Add what you run to find out whether that includes you.
EPSS puts the chance of exploitation in the next 30 days at 0.55%, higher than 45% of scored CVEs.
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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.
- CVSS
- 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- CWE-770
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- 0.55% (percentile 45)
- Assigned by
- VulnCheck
- NVD analysis
- Deferred
- Record last updated
- Oct 18, 2026
- First seen by InfoSec Signals
- Oct 11, 2026
Affected products
mark3labs mcp-go mark3labs:mcp_go (from the name) | through 1.2.1 | CNA record |
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
- https://www.vulncheck.com/advisories/mcp-go-through-1.2.1-denial-of-service-via-unbounded-post-body-bufferingthird-party-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.