CVE-2026-108859: Allocation of Resources Without Limits or Throttling in mark3labs mcp-go
Description
CVE-2026-108859 is a high-severity denial of service vulnerability in the mark3labs mcp-go library versions up to 1.2.1. It occurs in the StreamableHTTPServer.ServeHTTP function, where remote unauthenticated attackers can exhaust server memory by sending oversized POST requests. The server reads the entire POST body via io.ReadAll before validating it, allowing attackers to send arbitrarily large or many concurrent POST requests to degrade or crash the server process.
CVSS v4.0
Score 8.7high
Affected software
mark3labs
mcp-go
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in mcp-go (<=1.2.1) involves allocation of resources without limits or throttling in the StreamableHTTPServer.ServeHTTP method. Specifically, the server reads the full POST request body into memory before any validation, enabling remote unauthenticated attackers to send arbitrarily large or numerous concurrent POST requests. This can lead to memory exhaustion and denial of service by degrading performance or causing the server process to be killed due to out-of-memory conditions.
Potential Impact
Successful exploitation allows remote unauthenticated attackers to cause a denial of service by exhausting server memory resources. This can degrade service availability or crash the server process, impacting availability of applications using the affected mcp-go versions.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, consider implementing external request size limits or rate limiting at the network or proxy level to mitigate the risk of memory exhaustion from oversized or numerous POST requests.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-10-11T13:06:49.278Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6acb93d32cdf04f656d7076f
Added to database: 10/11/2026, 13:49:07 UTC
Last enriched: 10/11/2026, 14:03:24 UTC
Last updated: 10/11/2026, 21:33:08 UTC
Views: 17
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