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Back to active CVEs
High · CVSS 8.7CVE-2026-108859

mcp-go through 1.2.1 Denial of Service via Unbounded POST Body BufferingCVE-2026-108859

Answer in brief

CVE-2026-108859 records a High severity (CVSS 8.7) vulnerability in mcp-go through 1.2.1 Denial of Service via Unbounded POST Body Buffering. The current sources do not mark it as known exploited. The current feed maps mark3labs/mcp-go (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 11, 2026Updated Oct 11, 2026Source checked Oct 11, 2026First seen by HOL Oct 11, 2026Material review Oct 11, 2026
Upstream Advisory

Key facts

Risk
High · CVSS 8.7
Exploitation
Not marked as known exploited
Affected software
1 mapped package or product
Fix availability
Not reported

Why this deserves its current priority

CVSS is 8.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps mark3labs/mcp-go (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
PackageAffected rangeFixed version
mark3labs/mcp-gogeneric>=0 <=1.2.1Not reported

Recommended response

  1. 1Check inventory. Check lockfiles and deployed manifests for mark3labs/mcp-go.
  2. 2Review the reported fix. Monitor this advisory for an available fix and review any installs of the affected package.

Evidence timeline and material changes

  1. Published upstream

    Oct 11, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  2. Source modified

    Oct 11, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  3. First seen by HOL

    Oct 11, 2026

Sources and claim methodology

  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
  • Source referencehackmd.io
  • Source referencevulncheck.com
Upstream source 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.

Quoted source text, attributed separately from HOL analysis.

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  • erzhongxmu Jeewms Autocomplete Data JeecgFormDemoController.java getTreeData sql injectionSame generic ecosystem
  • hyper-mcp through 0.8.3 OCI Plugin Signature Verification TOCTOU Race ConditionSame generic ecosystem
  • hyper-mcp through 0.8.3 Improper Signature Verification of OCI WebAssembly PluginsSame generic ecosystem
  • thClaws through 0.141.0 Symlink Following File Write via POST /v1/inputsSame generic ecosystem

Record context

Vulnerability class
Tool Poisoning
EPSS
Not reported
CWE IDs
CWE-770
Source
CVE List V5
Source checked
Oct 11, 2026
References
4 linked sources
Open source record